I think it depends a little bit on you as an individual, and how you feel after your OW class. I went straight into AOW because I didn't feel remotely safe to dive without an instructor right after OW (remember, this is the PNW -- cold water, poor visibility, dry suit). The extra five dives really were necessary for me to get oriented and solidify very basic skills. The AOW dives were essentially just additional OW checkout dives, which one could argue I probably should have been required to do before passing in the first place.
If you feel as though your basic skills are OK, then my advice? Dive, and find a mentor. There are so many things you can address -- getting your weighting right, getting your weights distributed properly, working on not using your hands and improving your kicking efficiency, etc. Any good, experienced diver who likes to help can assist you with such things.
I've done AOW (already discussed) and Rescue, which was a good course and I would recommend it. I've also done Fundies, which was a superb course and a very good investment of time and money, but I don't think you get your money's worth out of it until your basic skills are reasonable. If you can't swim a pattern in 15 feet of water without losing buoyancy control, you aren't going to get very much out of the more challenging parts of Fundies. And, although the ideas of weighting, trim, and propulsion ought to be universal, the specific procedures for things like air sharing are equipment-dependent, and only really useful if you are going to adopt the Hogarthian configuration.
So that's my two cents' worth -- the biggest thing is to get in the water as often as possible and get progressively more comfortable with buoyancy control. Get your weighting right, and your weights distributed properly. Get some advice and support from a good, experienced diver (or more than one!) When you have enough experience, take Rescue, and consider Fundies if you are DIR-inclined.