In lane, put the first keg under your own feet more often than on the opponent, so they have to walk into barrel-plus-passive space instead of getting a free chase after you spend your zone on routine poke
Before level 7, win with self-kegs and simple doubles; after 7 and especially 13, Gangplank's barrel timing actually starts threatening barrel-auto-second barrel-Q patterns and walk-up or ghost-barrel detonations that opponents have to respect
Gangplank's better games usually come from pushing one more side wave before the grubs, dragon, or Baron fight, then using R or TP so the enemy has to cross a keg chain or Barrage line to enter at all
Leave side when the next wave stops being worth more than your setup time. If dragon, Baron, grubs, or Herald is about to matter, shove first, then move before the fight starts so your kegs are already claiming the entrance instead of arriving after everyone is in melee range. Stay longer only when no real spawn is coming and the enemy still has to answer you with someone you can safely keep pinned to the lane. If the side opponent can just sprint at you or force a fair duel, your window is usually over. The useful habit is to think one wave ahead, not one fight late.
Every few seconds, Gangplank's melee strike will set his opponent on fire.
Shoots target, plundering Gold for each enemy unit killed.
Eats citrus to cure crowd control effects and restore Health.
Gangplank uncovers a powder keg at target location. If he attacks it, it explodes, spreading the attack's damage to enemies in the area, slowing them.
Gangplank signals his ship to bombard an area, slowing and damaging enemies.