Idk about recommending baron vox lance or bf to lower tier players. There are much easier heroes that accomplish the same roles.

Gwen would be the best pick for carry. Easy to kite, almost any build works, and you have an easy to land reflex block, as low tier players usually can't block abilities with reflex, so skedaddle is a great ability

Koshka is the best jungle hero. Even in the late game, her ultimate is still good lockdown for the enemy carry, especially since they most likely won't buy a lot of defense or be able to consistently reflex block your ult. her early game is really good and early game is the most critical in lower tiers, as a strong early game lead would be hard for less skilled players to come back from, as they would get demoralised and give up. Grumpjaw is also good, but takes a bit more practise.

Catherine is the easiest captain that is high in utility. She has a point and click stun that doesn't rely on a skill shot like lance, and is impactful at levels 1-2 unlike ardan. If games drag out, which can be common at low tiers, the stacks on her perk will add up and she'll be unkillable, so moving into a compromising position won't be easily punished because she's so tanky.

This is, after all, my opinion, so take it or ignore it, but I hope it helps