if you don't know what to main...
Champion Select
If youre a jack-of-all trades, know alot of champs like them all cant choose one, cant play a champ more than 2 games in a row, just use this. It show you optimal picks for your role with a score showing how much better that champ perform in a specific matchup. Choose champs you know tho dont pick blindly. It use plat+ stats but it work in any elo tbh and it dont use only win rate, also game-specific things.