Im new to LoL

You should go to OP.GG and get an idea of the meta by looking at Win Rates and Pick Rates (ban rates too but I don't usually do it). Then, you get an overview from those champs and you can kinda see what's good as items, runes or whatever else. Also, you should watch some streams on twitch and see what the pro players do, as in movement, positioning, map awareness, etc.