Just a suggestion for people who love playing Gangplank, Yes going against ranged champions is a toughie, but everyone has their counters.
My best suggestion is when you're Gangplank in lane VS a ranged Champion (such as teemo or vayne for example) is to place a series of barrels.
If you're poked out under tower, Place a barrel or two back behind, or beside your tower out of range of their AA so they're unable to destroy it, letting it degenerate to one hit, so you can pop it. When they get close, place a barrel under them that is linked to the ones near/beside your turret and immediately Q, or AA the barrel under your turret to set off the chain reaction. Another suggestion is placing a barrel in one of the three top side bushes out of sight, so you can immediately drop a barrel center lane (linked to the one in your bush) and set off the chain explosion. Grabbing a red trinket to remove wards that they may place to counter this strategy would be suggested.
As far as I remember you can have up to 3-4 Barrels at a time placed out, it never hurts to throw one under your turret if you see your lane starting to get shoved, or an incoming jungle gank, or a potential turret dive. Sometimes it's easier to play strategically and safe, then to go full out 'ham' mode against an opponent that can easily out range/damage you early game.
Not sure how much clarity this post brings, but good luck!