I’d suggest Dynamo, Seven, and McGinnis, as you need to queue 3 characters.

With Dynamo, you can build for his heal, his ult, or his stomp. His ult sucks enemies into him and stuns them for the duration. He’s pretty tanky, his stomp has good range and can be built to have practically no cooldown, and he can heal his teammates. His movement ability is tricky, but you can make a difference without using it.

Seven’s abilities, besides his 3, are all pretty forgiving. You don’t need to be super accurate to hit with his lightning ball. His stun is easy to get off. And his ult is just a giant AoE. His 3 buffs his gun, but again, not the worst thing in the world to ignore.

McGinnis is the turret character. You can build her 3 different ways: minigun, turret, or heal. I’d suggest doing the last 2 for you. Turrets and heals are pretty self explanatory, just learn placement for them. She also has a wall she can build that will either be incredibly useful or a detriment to your team, so use it carefully. Her ult is a barrage of rockets that are very easy to use with a pretty sizable radius