I know I am not the best Katarina player but this is a basic guide that will help any Katarina player. I've been playing Kat for a while now. So I think I would have at least one thing new you can use in your skills for Kat. Enjoy!

If you understand what this is your already on your way to become a decent Kat player. If you know shunpo resets you can shunpo three times in a fight and dealing the most damage out of it. Here are two situations:
I q the enemy and shunpo to the dagger dealing damage.
I q the enemy and shunpo to the enemy. And then pick up the dagger.
Which one is better? Well obviously the second one is better. If you shunpo to the enemy and then pick up the dagger you do more damage than just picking up the dagger. So always shunpo to the enemy and pick up daggers for the reset. If you know how to use your daggers and shunpos wisely no enemy can get away from you. The gap close is insane.

Kat has one of the most bursts early game. She can deal a lot of damage. Here are some combos that use her abilities to the FULL potential.
Basic Combo:
Shunpo to the enemy. Drop w. Pick up w. Q and then shunpo to enemy. Pick up dagger. Shunpo again. Use ult in any of these segments. Use your shunpo to finish the enemy. Even if you are ulting use your shunpo to finish the enemy. If you are shunpoing a lot it will confuse the enemy and it makes you unpredictable.

Poke Combo:
First you throw your dagger and see where the it drops. If you see that your enemy is next to your dagger. Drop your preparation dagger. Then you shunpo to the dagger next to the enemy. And shunpo back to the dropped dagger u left. If you want to auto the enemy if you think you can get away with it go for it. Try to make a good trade because the enemy could attack you while u shunpo to the dagger. So only do this when you are safe from his or her attacks. This works especially on squishy mages. You can use the shunpos to dodge skillshots.

How to Wall-Jump:
This doesn’t work on all walls. It only works on the skinny ones. Drop your w dagger to the wall. Walk away and shunpo to the corner of the dagger that faces the wall. If done correctly, you’ll end up under the other side of the wall. You don’t even need ur w dagger. If you see the green plant next to a skinny wall if you shunpo to the corner precisely you can jump the wall.

Diving:
Definitely don’t dive if you are under six. Only do it if your jungler is there or the enemy is really low and you can maybe shunpo or flash out before you die to the turret. However late game Katarina can easily dive under turret especially if she is targeting squishies. If you use your combos and kill the enemy and the shunpo back to a teammate. You can only take one turret shot and get one kill. This takes practice and speed and accuracy. Kill the person without getting cced and shunpo or flash out as fast as you can.

Katarina is literally the teamfight assassin. Her passive especially. If she gets an assist or kill her abilities reset. Make sure you aren’t the first to enter the fight. Katarina is the best clean up champion. Don’t be the person to engage the fight. After you see that the enemy has used most of their cc abilities then it would be the perfect time to all in and clean up. And also if you have cc on your team you can use that as an advantage and ult, making the most of it. Make sure you don’t ult but then the enemy flashes away. Always ult when they have no escape so you can get the full potential. This is the big tip here: ALWAYS FINISH YOUR ENEMY WITH SHUNPO. If you are ulting. Break your ult and shunpo to kill the enemy. And kill all your enemies with shunpo if you can. It will make it seem you are jumping all over the place (make it look fancy unless you in a desperate situation). And it will make your enemies really confused. But, if your team is about to get aced, finish them with your ult, no fanciness, all savage.

This is especially annoying. Sometimes you can’t burst them down because they can burst you down too. What you can do is try to play passive and strike at the right moment. If you are fighting an assassin try to dodge all skillshots and if you are ulted by them you might be as good as dead. Always save your flash for this. To get away from people that can burst u down. If you are going against an adc that is kiting really well (vayne) and they can burst you down really hard. They can auto you to death before you can even get to them. Therefore if you get caught up, you can flash out of auto attack range and then shunpo back to them. What this does, is that it makes the enemy click on you twice to try and auto you which can mess them up which gives you a chance to burst them down.

If you want to go all in, make sure you know that you can kill the enemy. To know this, compare your damage, cs, items, and KDA.
You can use plants to your advantage. If you are running from the enemy in the jungle shunpo to plants to increase your gap or to even dodge skill shots in a fight.
In the laning phase, Katarina has the best harass so make use of it.
Once you get a few kills in a lane you can start roaming other lanes. Especially after 6 you have your ult and you can easily burst down ad carries and squishy supports.
Sometimes in teamfights your shunpo is on cooldown. And the enemy is next to a dagger. And only if you could pick it up to kill the enemy. Thats why you got flash. Flash to the dagger. This is really useful if you really need a shunpo reset.

Thanks for reading! Katarina is a really fun champion and is worth the time invested to play and get better at her! Stay tuned because there will be updates frequently!