My initial instructor advised us to give it 50 dives to get comfortable with our bouyancy control. At a basic level I found that to be a reasonable baseline. But keep in mind that it boils down to "compared to what?" ... buoyancy control is relative to what you're doing with it, and how you measure "comfortable" ... I'm coming up on 2900 dives, and still working on getting better with my buoyancy control ... there will always be ways for improvement if it matters to you.
You do not need to take AOW to improve buoyancy control ... many (most?) AOW classes won't even address the problem ... they'll just provide you a few extra dives under different conditions and not really focus much on your skills at all. If you want to improve your buoyancy control, seek a class that focuses on it ... a well-taught Peak Performance Buoyancy class, a skills workshop, or one of GUE or UTD's entry-level classes. These classes will spend a lot of time and effort going through the equipment and techniques that help you improve buoyancy control, without all the splash of "experience" dives.
The other way, of course, is to dive, dive, dive ... find a mentor who can take you diving. Pay attention to your weighting, trim, and breathing ... and you will improve through sheer effort. That's probably the most fun way ...
... Bob (Grateful Diver)
totally agree with bob. ur buoyancy control has got nothing to do with taking aow classes. perhaps it adds on to ur total number of dives and hence improving ur buoyancy control but more imptly as bob pointed out is to dive, dive, dive. as in most sports, u need to practise, practise, practise and if u can find someone to give u abit of guidance/pointers along the way so much the better. most imptly hv fun along the way