You can pretty much make any kind of game you want to:
The Last Space 9
Flow Motion
Random Realms
I very much like the flexibility of DBPro (and AGK) and the fact that it doesn't force the user to make a particular type of game.
My advice is not the buy anything just yet. Use the free version of DBPro first to see if you can get on with it. I made Purple Complex (see the link in signature) using just the free version of DBPro and Sparky's collision dll.
The other reason to hold off is to see if any new updates came out for DBPro (there might be some off the back of FPSC Reloaded or there might not or there might be a paid for upgrade or not, it's difficult to tell what'll happen) or to wait to see how the 3D commands in AppGameKit turn out. I personally quite like the current 3D command set, they are limited but you can still make a pretty cool game with what's there.
Or, if you want to predominantly do 2D games then I would suggest using AGK. Get AppGameKit V2 as I think it'll more likely get get all the cool new upgrades and the new editor is pretty good too.
I came to DarkBASIC having used QBASIC for a little bit and found the transition pretty easy so you should be fine.