Glad to hear you've decided to buy Darkbasic Pro, good move.
I myself have owned Darkbasic Pro for a couple of years now but had no previous experience in programing at all, and I must say I struggled like hell to get my head round just the very basics, but with alot of help from everyone here and reading manuals which bought, I am slowly beginning to grasp the fundamentals of the language ( well I think I am. lol )
I purchased:
Beginner's guide to Darkbasic Programming by Jonathan S. Harbour
which teaches the use of 2D and 3D commands, and covers mostly everything you need to know about the commands used in the language. A bit fast paced for the beginner, but an excellant reference manual.
Hands on Darkbasic Pro Volume 1 by Alistair Stewart which is dedicated to 2D commands and is a self study guide to programming in Darkbasic, I must say I'm impressesed with it, and it has taught me alot, although I don't get that much time.
So I'm still only half way through it yet, but if you have basic knowledge of programming you could probably wait for Vol 2 to be released, which is very soon, which covers 3D and would probably be more appropriate for the game you have in mind.