A few traits you should look for: 1. A champion you enjoy and know how to play well 2. A champion who takes advantage of common mistakes/failings at that ELO 3. A champion who isn't constantly going to be banned.

Obviously, the first trait is the most important and the actual champions are going to vary depending on the player and the current meta.

If I had to make a suggestion (or as an example), I'd recommend looking into Heimerdinger and see if he suits your playstyle: - He's rarely picked or banned. As such, you'll be able to reliably secure him and many of your opponents will lack experience facing him (which might lead to them underestimating his damage and easy kills). - He applies significant objective pressure with his turrets, helping zone opponents while killing Dragon/Herald/Baron/towers. Heimerdinger, with the help of one other player, can kill Baron and Dragon pretty quickly which helps in disorganized environment; if your team won't group, you just need one other person to kill the objective while the rest distract the enemy team. - Straight-forward, powerful laning phase leading to reliably mid-game strength.

The laning phase is especially nice. As you'll often be pushing with your turrets, you'll (1) have priority to roam when fights break out nearby, (2) help prevent your opponent from roaming (or forcing them to miss farm), and (3) occasionally bait the enemy jungler into ganking you (which you might be able to turn into a kill).

Heimerdinger's ultimate is pretty flexible too. If the enemy team is trying to dive into you, Ult-Q will deal a significant amount of damage to them. If the enemy team is trying to run away, Ult-E will help engage a fight or disrupt their backline.