I wouldn't rush in to buy a diamond membership until you've been here for a while and tried it out. Gold is a good starting point and, if you want more, you can work your way up.
With diamond membership you have unlimited access to Chess Mentor, an excellent training program, and access to all the training videos as well as all the benefits that go with the lower priced memberships -- access to tactics trainer, unlimited tournaments, and so on.
can u tell me how does diamond membership improve playing chess on chess.com????