By all means, if you want to make games it doesn't really matter where you start. While learning c++ leaves you with almost unlimited possibilities it isn't a "must have" skill unless you want to work in the mainstream industry or go on your own building or modifying a more advanced engine.
It really irks me when someone asks about making a game and someone else says "learn c++". There are people out there who have made money with games made it simple languages like Dark Basic. They aren't millionaires, but many have made enough to live off of.
As for Dark Basic vs. Liberty Basic go to
http://darkbasicpro....mecreators.com/ and see for yourself. It's main advantage is that 3D features are integrated into language, with BSP support and the like. Features which Liberty Basic lack (at least the last time I looked at it).
Also, there has been a new book released for it that works with all the features of the language. 700+ pages and it's part one. Part 2 later this year. (You'll need the book, the manual that comes with DB Pro is useles.)
Last you may want to look at Blitz3D as well. It quite similar to DB Pro. I own DB Pro and while I like it's features there isn't a lot of useful organised information on using it without the new book (which is pretty pricy). I'm thinking about getting Blitz3D when I can afford it.