• first things first: do NOT go PvP until you feel comfortable. it's okay to play against bots. test the map, the items, characters you think look cool, fun or nice. increase the difficulty level when the beginner one becomes easy to you.
• when you play your first PvP don't feel bad if it goes terrible. Everyone, and i say this with confidence, everyone sucks absolute ass in the first pvp match they do. -LoL has very competitive ppl and yk, insecure ppl, so they might flame you. if youre sensible to that, mute the chat .
• there's a character you like, hurray! you want to get good at playing this character? search for guides, there's tons of them. there's this guy on youtube that summarizes a champion's kit in 3 minutes. we're in s14 right now however, so there's some items in a couple guides that aren't there anymore. keep that in mind
• dont focus on win rate or KDA, focus on having fun and get experience. after that you can focus on winning
• if you get skins in chest of characters you're sure you wont use, keep them in the loot section until you have 3 skins, then you can roll into another one. (if you dont have orange shards tho just exchange the skin for shards lol)
• hit a minion when their health is low for epic gold! (this is, like, something that everyone fails to do which is funny)
• DONT MISS CANNONS PLEASE KILL CANNONS THEY GIVE YOU GOLD but dont feel sad if you miss one, a new one will come by so you can destroy it
• dont play jungle. im serious. don't play jungle until you get experience in this game.

i ended up rambling a lot mb but i hope this helps. im not a grandmaster + or whatever but these helped me for years !