I play all roles, but weakest role being jungle :/
I'll try name some "OP" considered champs,
Malphite - tank with ridiculous game changing stun,
Hecarim - annoying as hell when against it in the jungle,
Rumble - annoying AP top
Diana - ridiculous AP carry if she gets a few kills (you might like)
Taric/Thresh/Sona/Blitzcrank - support's I'd play if I was forced to play one
Lee Sin - strong top or jungle,
Elise - Stupidly strong top,
Akali - Stupidly strong top / mid,
Thats all I can think of off the top of my head right now
I don't think theres really any "Pro" tips I could give, other than don't play too defensive, 80% of my loses are from team mates being afraid to engage when the ods of the fight are in our favour,
You can try using sites to "counter pick" champs, but I find most of the time I just prefer to play what I want to play
as long as it's not ridiculously weak against the other teams picks