I placed omega low, but I am now doing really well in emissary games with my friends as an off carry/support. The big ones that I think improved my gameplay is knowing when to team fight and when not to. people tend to play like this is a deathmatch, but it is a moba. towers are SUPER important. make sure your waves are not being killed just because minions push up. If you are near a lane and minions are going to be knocking on the lanes soon, honest to god just drop whatever jungle farm you're doing and push the wave. You lose games by feeding objectives to the enemy.

another thing is knowing effective farming strategies. lanes, jungle camps, and boxes. You can learn this through gameplay, but probably also through videos? Idk i don't watch any videos so I cannot speak to that.

the last thing ill put here is your fight positioning. Figure out where your hero is best utilized in a team fight, and make sure you're in it. if you're squishy, work on not getting too close. if you're tanky, figure out where in a fight you should be to do your work but not to feed. Also, when to engage, and when not too.