Sentinel: Sage is a no brainer most of her utils benefits her teammates instead of dealing damages. The only troll thing they can do is slowing ur whole team + walling flank, but overall shes great. Cypher would be my next pick if you want to start with sentinel since his util is relatively easier to learn compared to KJ setups (Not including sneaky one way cages) but you are not going to be as great as the others in terms of lurking and creating breaches for your team.
Initiator: DONT play a flash initiator like Skye or Breach if you just started you are going to get a lot of complains if you flash ur teammates. My pick is Sova. Even though Sova has a very high skill ceiling and very hard to master he is acc very easy to start as a beginner imo because his dart can just be shot on any walls on site and get some info in the process.
Duelist: No brainer play reyna. Her util benefits herself > than her teammates so you don't have to worry about util comboing with ur team. Phoenix is good as well but ur flashes will a nightmare for ur team if you dont know how to throw them correctly.
Controller: DO NOT instant lock smokes in rank, but if you really want to try play brim. Clove can be good as well.
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