It took about two years for me to get on the level of the top 50 best fighter pilots in AH. I didn't consciously study ACM, I just saw what worked and what didn't. Things would have progressed much faster if I had picked up a book on fighter combat.
But that being said, I was a very good pilot. The AH pilot that I had the most trouble defeating was Shane. I think hes probably the best, ACM wise. There was also this guy who was some kind of P-47 fanatic, he gave me alot of trouble too.