Okay, this is my Gangplank build I use in both SR and TT. Personally I find it better in TT but it has the chance of working in SR too. In this build you focus mainly on hitting really hard with powerful critical hits and nobody can really stand up and 1v1 you. Unless, of course, that is Mordekaiser, because we ALL know Mordekaiser is pretty much un-beatable in 1v1. I know this build isn't the best and I never really expected it to be. It's just a build that's helped me win a decent amount of games and it's really a nice shine in 3v3 games.

Of course there are some pros and devastating cons to this build.

Pros

You can 1v1 all champs just about.
Anyone trying to run away probably can't without Flash/Ghost/or playing as Yi.
You're really hurtful in the laning phase.
Carry champions, like Ashe, will stand no chance.
Can break out of CC.

Cons

You will probably be focused as you are playing a pretty tough champion.
If you have a terrible laning partner, this build probably won't work.
Will not allow you to carry those nasty players who aren't doing too good :/

I like to say Crit damage and Crit strike runes because of his Q being able to apply on-hit effects, making crits very awesome on GP. When you're level 1 with some crit chance to kinda dish out so much damage with so little mana cost and without putting yourself in too much danger you should be fine.

Of course there are other runes you can use like Physical Damage runes or maybe some health runes. It's really all according to what you feel the build is lacking or may need. I usually run either all Physical Damage runes or my crit runes because those are what I see to be really useful for Gangplank.

I like to go 21/0/9 because you can get some nice damage from Offense while getting that super helpful Greed in utility so that you can some extra gold to help you buy the items on this expensive build D:

Other methods could also be to get some Defense points instead of offense so that you have better survivability and that nice chance to escape ganks or tower dive.

I like to bring Exhaust and Ghost because with Exhaust you can easily take down a carry's health and reduce their damage a LOT while using Ghost to either catch someone or move to defend a tower.

Other nice choices would be Flash because it would allow you to quickly flee if your health is low or to escape that nasty Jarvan who keeps picking on you. Ignite is also a good spell because it will allow you to throw down some true damage on someone or help you pick up a nice kill if they kill you first.

I like to start with Doran's shield for the extra HP and Regeneration which is very helpful for Gangplank so you can conserve some mana to use his W for when you're CC'd. I like to buy 1 Long Sword and then get boots and the second long sword after that so that I can move around some before having Youmuu's Ghostblade. The reason I like to get Youmuu's is because it kinda has some crit chance and damage, thus saving you from having to buy some phantoms. Then I try to get a B. F. Sword for the nice damage that it adds to his Q. Then upgrading the Boots to the Ionian Boots for the Cooldown Reduction which is really nice. After buying pickaxe you may want to get a giant's belt so you can stay alive longer which will really help you out if you're trying to defend or if you get ganked. Afterwards getting a nice Cloak so that you can finally build yourself into an infinity edge for even more painful crits! Then you wanna try building that Giant's Belt into a Frozen Mallet so you can have some more health and slow them a lot :D! Then for the last item just try building a Bloodthirster for that awesome damage and life steal.

I personally find GP to be good with quite a few champs in lane. I will explain why for some of the champions.

Shaco
Now, Shaco laning doesn't always sound good but if you have a great Shaco as your lane partner you guys will dominate the other team in your lane. Why? Simple because he has that nice little Two-Shiv Poison move and his Decieve. You don't have to face check brushes! Just make sure to try and split your lane kills some.

Mordekaiser
Well, put simply Mordekaiser can kinda eat away at the enemy champs and be a nice little tiny tank for you, and we all know we LOVE people to take shots for you. Not only that but he has excellent damage output mid and late game with nice early game. Just make sure you kinda take a few of his kills because he's Mordekaiser and he can do really well with assists if he's good.

Renekton
Renekton is just a perfect champion if the player is good. He has a stun too which is a nice thing for you to have with you seeing as you can Q the enemy to death no problem. Plus, he can use his Cull the Meek and be able to be a nice Tanky DPS for your lane. Always help him get a few kills.

When a tower is being attacked by minions and all enemy champs are elsewhere, take the advantage and kill some minions with your Parrrley so you can get some really nice bonus gold for those really expensive items so that you can take out an Ezreal who thinks he's all good and such when you Parrrley him a few times. Just remember to spam Q on ALL enemy minions with low health. Always try last hitting with it.

Pretty much you'll be walking around the map finding some stragglers in the jungle and kinda shooting them really hard with your Q and easily chase them down and kill them. Or to take out that evil carry that loves sitting in the back killing all your teammates.

You could also do what I love to do and kill jungle champions while they're jungling early game and watch as you get some nice extra gold instead of that greedy GREEDY blue/red buff.