Well i might save you some money, but the better coach is yourself and internet.
Just watch youtube videos and learn the basic thing and train yourself on practice map like aimbotz ect.
- For the aim, try some map on the workshop (Recoil control, shooting bot ect)
- The gamesens come with the time and experience
Maybe check TheWarOwl on youtube, he's making some tutorial sometimes
here's a playlist :