Hello first play safe as Nasus. Farm under tower and try to get xp from minions. Try to always land your Q on cannon minion. After lvl 7 it is free win fight top 1 vs 1 Carnarius said that in his build. I defend a lot and tell my jungler not to gank. Instead the jungler can go dragon with mid or botlane.

When you farm minions you want to lasthit with Q on the minion(stack it) and then go away a little bit from te minion wave. Fleet is good when you want to get away fast from the wave. Because the enemy wants to punish you and do dmg while you cant do anything against them.
Start with defending. Q (Lasthit) then walk away a little. When you get your Q back you can repeat.
But be careful so they dont punish you hard and maybe kill you. I only farm when it is safe.

Defend a lot to lvl 7 or 9. Start with giving the enemy the farm. Then when minions is under tower it will be a cannon if not fast pushed lane. Take the cannon. Then repeat it until you get lvl 7 or 9. When you are lvl 7 or 9 try to kill enemy. Make sure you eather have sheen and boots or so. OR that you two (You and enemy) have not recalled yet. You must have same hp as your opponent or if he is lower then even better. NEVER go in with lower hp, only under YOUR tower. 1 When you got the kill: Push a little bit or recall, buy items and walk back to toplane. 2 If you died: Try to understand why you died and how you can prevent it from happening again. Did enemy flash? did enemy have a lot of healing? if they healed a lot then buy bramble when you can. If they flashed then wait to next ult and do the same, go all in.

When you get tower plates try to get 1 or 2 and then back, recall. Because sometimes you overstay and will get killed by enemy jungler, midlaner, support or the toplaner tp back behind you. So try to push lane after you get a kill. 1 If your minion wave is big: go for 1 or 2 tower plates. 2 If your minion wave is small: Then recall (b).

Try to save your tp for dragons so you can help team get dragons easier. The best thing to make a perfect tp for dragon is to think before going in. Can I push this wave and get first tower? OR should I freeze and tp dragon? 1 When you want to tp: Tp only when your team needs you. If they don't need you then don't tp. If they need you and start to ping a lot then tp.
1 When you tp for dragon: Go for the one that does most dmg or has the biggest bounty with team. Go all in on enemy Choose one enemy to kill and kill him/her, then start dragon.
2 When you walk from base to dragon: Do as 1 but save tp after teamfight don't help team with dragon, recall instead or walk top. If you choosed to recall: tp back to lane if you see a big wave (cannon or many minions) or walk if you want to save tp from dragon.

Try to splitpush and save tp for objectives and teamfights. If you have tp then be on the other sidelane of the objective. I will tell you why.
1 Dragon and you have tp: Stay toplane. Give the midlane and the botlane for team. If 2 or more shows up in toplane, then it is FREE DRAGON for team to take. Don't die just run away and keep them top so your team can go easy dragon.
2 Baron and you have tp: Stay botlane. Explain to adc why you need to be botlane. Same as dragon, but sometimes you want to stay botlane because. If team gets Baron then enemy team will be baron and they are far away from you, so it is FREE BOTLANE TOWER. Sometimes you can even push to inhibitor (if enemy is dead). Try to always play safe with baron. Stay in lane and let cannon minions do dmg to towers.

Save your Q. Ult (R), E, Q, W. OR Ult(R) Q, E, W, walk Q.
1 You have full hp and play against a fighter: Think of what is the strongest in enemy. If for example Darius, then he does a lot of dmg and can heal if he lands his Q. He can escape with E and W. Then Ult (R, for dmg redruction and for lower cooldown on Q). Ghost so you can catch up with Darius. W so he Can't escape. E in the path he will walk in so you do more dmg if he is in it. Q right after E. Walk if he walks. Basic only if he stands still ELSE. Walk more in front of him so he has terrain to move around. Q again. walk more Q again. Walk. Now he should be under tower if he ghosted and thats ok because he did run away from you so he did not do much dmg to you so you can dive under tower and W E him then Q. Now your Ghost will be Extended if you killed him so you can get out of tower faster.

2 You play against an adc and you have ghost: Stay under tower wait till lvl 7 or 9. Make sure you have taken cannon minion before you fight adc. When only caster minions is left then go all in on adc. Ghost and Ult (R). W, walk to enemy adc. When you are close E and Q. If you play against Quinn then SAVE flash and Flash AFTER she jumps away from you. It will be easier kill if you have right runes, so you can catch up to her.

Save E in farming. Only E cannon minions and some melee minions if you need to b after.
1 Only E cannon minions if you cant stack with Q, so you don't miss 90 gold from cannon minion.
2 Only E melee minions (+2 minions)if you cant stack them with Q.
3 If lane is pushing then E when minions is in the middle of the lane. But ONLY if your minion wave is bigger than the enemy toplaners minion wave.
4 When you are going to recall try to get some minions before recalling so you can buy maybe 1 more item.

1 You need 700 gold for first recall so try to defend a lot so you dont die. If you recall and have less than 700 gold then you can maybe buy boots so you can get safer stacks and gold for sheen. But if enemy has no movement then just save for sheen.
2 You need then 950 gold for Ionian boots for cdr.
3 You need 800 or 1200 gold for kindlegem and health 800g + 400g (items)
4 you need around 1800g for divine. I will do more math for this.
So basicly you will recall maybe between 4 or 5 times. After that you will be strong.

1 When you push and minion wave is under enemy tower and you are fed. Then you can go for rift with your jungler.
2 When you got tower and you can't follow minions deeper in to enemy tower in map. Then go for rift.

When you play against Yorick push in the beginning, because he does not so much dmg in lvl 1. When he gets lvl 3 back off, defend.
When you get to lvl 6 then go all in on him. Make sure to slow him so your velocity starts to work. Chase him.
Q, walk Q, walk, Q walk thats the combo. If he is under tower dont chase. Go for minions instead. When your minions is under his tower recall. And then walk back to lane or tp.

Defend and wait to lvl 7 or so.
Splitpush.

You want gankplank to use hiw W (healing) so you can W him and get bonus movement speed.
Start with W and walk towards him, dont go all in. Let him W so he has cooldown on his W.
Then after he W wait so your W is up, W him and go all in on him. Now he cant escape, only way is if he got flash ult even then you can still kill him.

Remember where he ulted and placed his mushrooms so you dont step on them.
After lvl 7 when you are under tower you can go all in on him. If he has ignite be careful. If enemy jungle is missing be careful. But if his ignite and jungler is botlane it is free kill just take velocity in runes so you get that bonus ms when you run towards him and you can activate ghost.
When you catch up on him remember does he Q first or auto then Q?
If he auto and then Q then you can run to him and Q then run with him.
While his blind effect is on you your Q is on cooldown. You cannot use it and even if you had Q you would miss it bc teemo blinded you.
If he instantly Q when you walk or run towards him just run with him, dont walk on his mushrooms. after 1 sec of blinded(remember we got LEGEND: TENACITY in runes) then we can start to Q him, maybe do some autos and chase then Q, repeat and now your CONQUEROR in runes should activate and your last Q can kill him.
If he flashed thats ok go back to your last caster minions and stack them.

First go in in brush far away from opponent. Wait 1 sec. Come out same spot you came in.
Then go in in brush far away from opponent. Walk in brush towards enemy. Come out in the nearer end of brush towards enemy. Now you will suprise him/her and you can ghost and go all in if you want OR just make enemy flash away from you.

Try to stay in lane longer and get minions and try to push so you can recall and dont miss much xp and gold.
When you have got sheen and some cdr hp you can stay in lane and wait so you can afford divine.
Try to stay so you get to 14 mins so enemy cant get tower plates, then you can recall so they dont get bonus gold. But only if it is safe.

When you play against Gnar you can get 1 minion but you have to run away fast because if gnar does 3 basic attacks then he will do much dmg.
Try to stay under tower and farm, dont overstay when you are pushing.
When you get to lvl 7 or higher you can see if you got a opportunity or not to kill him.
If you see opportunity then go all in on him.
When you go all in on him he wants to jump on you so be careful so he does not go behind you so he can jump longer and slow you. So when he tries to run behind you run backwards. When he gives up follow Q, then see what he will do. Remember to slow him with W.

Play safe lvl 1. DONT GO IN. she will kill you if you go in her. Instead wait for lvl 7 or higher.
Remember Riven players like to bait with her Q. They Q wait Q wait and then jump Q on you. After they jump Q on you they got Q back with some cdr items.
So when you see riven wait for her to make a mistake. Something like she Q minions fast. Then she dont have next Q on redruction. And you can kill her.
I like to wait so she does that on minions in the middle or on my side of the lane.
If I die I might miss a cannon but I got tp so I can tp back to lane and get most of the minions.
Go all in on riven when she does a mistake.

Most nasus players will buy Frozen Hearth for mana and it gives armor.
So if you play a mage you will counter nasus. Then he will not have much mana and you can kill him easy.
Mordekaiser is a good option because he will buy Riftmaker that will give you some true dmg when you are in a fight for 3 seconds.
Mordekaiser can hit his Q on nasus and push, play very aggressive.
Mordekaiser got Shield so he can do 1 Q under nasus tower if he defends.
Nasus got 350 base moement speed, but does not build movement speed. So thats why morde is a good option if you play against nasus.
There are other champs that is stronger or better, but for me morde feels like the easy option.
Just push, Q when you ult after he ult you get some of his stats. Easy win lane and late game you got much area dmg that is good for teamfights.
Also if you 1 vs 1 someone your Q will do 2 times more dmg when it only hits 1 enemy.

You can check opponents in op.gg or porofessor.
You can also check wikifandom for the enemy toplaner you will play against.
You can play some champs that you feel like you cant win against so go and play a normal and then think of what is the strongest with the champ.
Example Illaoi loves tentacles and walls, so try to play in the middle of the lane or so.

When you backdoor look for tradings. Will you lose if you dont help team and go for tower and inhibitor or will you just lose a teamfight.
Backdoor is good when there is no objectives in game because when your team does 4 vs 5 then you can go for tower because there is no dragons.
When you see a opportunity to win but you will lose something also. If you lose baron for a win thats good. When enemy is at your base then you can tp to their base and ULT so your Q got lower cooldown.