I'm going to go against the flow and say DON'T do divemaster, unless you have a specific ambition to work in the dive industry, or to help someone teach.
Id agree entirely with that. A DM course is all about learning how to supervise others, very little is about your own diving skills. If you want to improve your OWN skills an entry level tech course like AN/Deco Proc etc is a far better idea.