as an ex- somewhat serious unite player, I'll give these few tips (based on what I knew about the meta back then, which is like a few months back, but barring any major changes they should still apply):
usually defenders are the easiest to pick up on, simple bc most of them just do absurd amounts of damage for how tanky they are. that's why i used to main trevenant, but stuff like slowbro also do high amounts of dmg in conjunction with their util to help its team stack more dmg. if you don't have an objective main, try some defenders
other than defenders, dragapult feels dummy easy to use as an attacker; it can hit through walls, phantom force is actualy broken, and it can midlane effectively as well. the specific timing and skill to play with phantom force does take some time to develop, but at least you dont have to worry about walls and have a fairy free cop-out if you get into bad situations (that being said iirc pult got nerfed when I left so idk about it anymore)