So far I am thinking these kind of builds are probably going to be the best.
Tankplank http://na.leagueoflegends.com/en/featured/preseason-update/8400-8437?build=30121162
Critplank http://na.leagueoflegends.com/en/featured/preseason-update/8000-8021?build=02101164
Little of Both http://na.leagueoflegends.com/en/featured/preseason-update/8400-8437?build=30221228
That's what I am thinking but love to hear others thoughts.
Rykagnar2 votesI really like those! I came up with kind of a wacky page - combines Sorcery and Precision.
http://na.leagueoflegends.com/en/featured/preseason-update/8200-8229?build=21122027
I figured this would be really helpful - with the Arcane Comet, hitting barrel combos or your ultimate will do increased burst damage, which I think is really helpful.
For the 2nd keystone, Manaflow Band really helps for in-lane sustain so that you don't have to back as often.
Absolute Focus, for the 3rd keystone, encourages Gangplank to play like the backline he is. It helps immensely versus tanks and furthermore bursts squishies. The extra AP also buffs his W quite a bit, which I think is great.
For the 4th keystone, since GP is a mid-late game champion, I chose Gathering Storm, just to encourage and to reinforce his strength as the game goes on.
I chose Precision because it gives GP bonus AD and AP. Presence of Mind helps him extremely well with lane-sustain, and Cut Down helps versus tanky team comps, and the bonus damage + armor pen on his kegs will shred them.
Kloqdq1 votesI think that kind of build would help for the Crit builds just as nicely :P. I am more of a Fighter/Tankplank type player so I valued the early stats over the scaling a lot more. For the Crit I liked the added mobility and slight sustain to help him scale but that build would smooth out his early game most likely.
Trap or a Trick1 voteshttp://na.leagueoflegends.com/en/featured/preseason-update#builder I kinda liked this one, gives me the best early game possible (probably, didn't read all of em) it allows me to get heal barrier tp flash or exhaust, depending on what I end up needing to survive, and a lot of healing, since I never buy any sustain. I also wanted to try the meteor move for his ult, but I think it dosent have a fixed travel time, so it would take years to reach bot lane xD
Kloqdq1 votesYour page didn't save btw XD
I was always a Grasp GP and the thought of Grasp plus stacking HP along with loads of just stacking across the board lets me have the early game I want plus a late game. Plus I can push my 1v1s and split-pushing power a lot more which I love.
Trap or a Trick1 votesYour page didn't save btw XD
I was always a Grasp GP and the thought of Grasp plus stacking HP along with loads of just stacking across the board lets me have the early game I want plus a late game. Plus I can push my 1v1s and split-pushing power a lot more which I love.
oh xD
TheZarTrox1 voteshttp://na.leagueoflegends.com/en/featured/preseason-update/8100-8112?build=10210128
I think this may be also a good choice for crit
. You will have a good scaling and a decent early sustain. But imo you can change "ultimate hat" with "absolute focus" for extra damage. Also "taste of blood" and "cheap shot" can be swapped. There may be a few mana problems before one can buy 
( not if one starts with 
) but it seems pretty solid to me. Got any improvments/thoughts on this build?
Kloqdq1 votesI would probably go for cheap shot for finishing damage since Barrels may not one shot and if you tag them with anything else the damage will be nice. taste of blood works too but I am not as big on it.
Hat I feel is the best change spot in the whole page in my mind. The tick on scorch just helps win more trades, the magic shield will help against magic damage a lot, while absolute focus will just amp the rest of your damage. I think that's a pretty solid page overall for GP. You do run the risk of being a little more snowball dependent but you should be fine.
Quepha1 votesBankplank but it looks like the link breaks if you use the final inspiration keystone.
Kloqdq1 votesI hear that one is a gold one with extended range and in which case, I will make Bankplank.
rework trundle1 votesI'm no expert, but why would you want AS instead of LS (the Legend stacks thing in Precision)?
Kloqdq2 votesAS increase helps with a couple of things. First it helps with CS'ing a lot. AS for cs'ing is pretty big and base 5% increasing to 20% is going to be really nice. It also increases your DPS in an AA trade by a fair amount. Each extra auto will help you kill your enemy that much faster which is good. The AS also helps taking turrets which plays to your ability to spiltpush.
I liked it over the other two stacks because tenacity isn't as powerful overall in my mind because of the way tenacity works so I valued the AS over it. The Lifesteal one has no value in it from the start and stacks really slowly with a very weak max. You would need about 90 CS to get 3% life steal when you could get 90 CS and get 14% attack speed. That is a LOT of AS at 10 minutes in where the life steal is really really bad.
The other big thing is we already have 2 forms of healing from just runes alone Fleet Footwork has a heal built into it while I took trumpih as well meaning I already have a fair amount of potential healing to be done. The LS just doesn't seem worth it in the slightest but I can't blame them for having to make it so weak. They don't want people to get 10+% life steal because then no adc would need life steal. But because it's only 6% vs a possible 20% AS, I'd rather the AS.