Quick tips for free
I'm just going to list a few things that have helped me throughout the past. Each tip will be very brief and if you want me to elaborate just let me know!
General: Ctrl+F shows ping without having to hover your mouse Disabling auto attack prevents the turret from targetting you if you get pulled into the tower with friendly minions nearby. Removing summoner names gives you more clarity Cleanse removes ignites true damage
ADC: Shift+right click=attack move. Master this and make it a habit. The minion wave will always target the closest enemy minion. Pay attention to this when last hitting to micromanage healthbars better. Last hit based on how many more minion projectiles it'll take to kill the enemy minion and not How much damage you THINK you'll do based on its HP. Press X to see your champions range. ALWAYS attack from max range.
Mid: Never spend mana on an AoE spell just to harass someone. Make sure you're achieving multiple things like damage+last hit. Don't stand on top of your casters. They can block you sometimes making it difficult to dodge AoE spells. Clear the casters safely with spells and last hit the melee minions. If you want to manage your mana effectively, limit 1 AoE spell per wave. Always trade damage. Never use your mobility spell. Save it for ganks no matter what. 99% of players rely on ignites true damage to secure a kill. Try bringing cleanse to counter this strategy. If you dodge Zed's Q when he ults you, you can avoid most of its damage. Position yourself next to a wall and wait for Zed's ult. When he appears quickly flash or jump over the wall or tower to avoid his damage. If you displace Leblanc's W, you can avoid all of its damage.
Jungle: Always start bot lane since there's more people there to help you with the leash. If you do red, blue, and 1 camp you will hit level 3. If you back right away you sould have enough gold to upgrade your machete and purchase a pink ward which can be used to guard your red jungle entrance for counter jungle. Gank when your smite is on cooldown. You're technically still gaining exp while you wait for a good opportunity to gank. Your second buff spawns around 7:15. If you smite golems 45-60 seconds before the next big buff, you'll have a faster clearing speed. Only waste your smite on wraiths. Free oracles is too good to pass up on. Place a ward on the enemy wraith camp to counter this "free" oracles.
Top: Always bring teleport And use it for counter ganks. If your enemy has ignite play passive. Hold on to teleport and use it to snowball bot. Don't overextend. Top lane is the easiest lane to gank.
Support: Pay attention to your ADC. If they're less experienced play passive. Ward tri-bush with a pink. Rush sightstone. Peeling for the ADC is your highest priority in team fights, not initiating. Always ward the jungle entrances with your sightstone. If your ADC is very unskilled, ask the jungler or mid for help in a nice way, "hey Vi, we're really struggling down here can you please give us a hand?" Exhaust the enemy ADC when he's ready to fight to the death, not immediately after you land a hook or any other form of cc.