Should I buy Gangplank - pls answer

He's fun I'd say yes

First of all have you ever played with GP before?

If not I would highly recommend to wait for a free rotation he's available in.

Secondly are you a top or mid lane player? Because these are the lanes he excels in. I'll admit I've laned with a GP ADC but he was a GP main and pretty much destroyed their team singlehandedly.

Lastly GP is a champ which takes alot of skills but if he is played to the best of his capabilities he can win gamea very easily. Chaining barrels is something you will have to learn extensively.