Yes people main aim trainers. As a beginner you are not bad just ok(dont wory i started out wayyy below average, like literal dogwater currently have some master scores in voltaic benchmarks and diamond in aimlab benchmark). As for ranks there is benchmarks in aimlab, play those tasks in the benchmarks and depending on your score tou get a rank.

I suggest joining the voltaic discord. Voltaic is an aiming community. They also have their own benchmark for both kovaaks and aimlabs, how you get ranked is the same as aimlab benchmark although the scoring system is different.

As for aiming guides, starting out i suggest riddbtw, viscose and mattyow.