Welcome,
@Dlw4456. You have probably joined one of the most Combat Mission savvy groups around.

How did you discover Combat Mission games if I may ask?
Please be patient with yourself trying to learn the game. It has a very high learning curve. It took me several months before I thought I understood it. Years later, I still struggle to play it really well. There are several CMBN tutorials on YouTube. Check 'em out.
Which title to buy really depends on what you enjoy and what you want to do. I personally don't play any of the modern time-frames primarily because it's of lower interest to me than WW2 and I just can't find the time or money for everything that's out there.

Most of The Few Good Men seem to favor the WW2 titles; at least those are the titles played most often H2H and in our regular tournaments. The mechanics are the same for all four (4) titles; CMBN, CMFI, CMRT, and CMFB. Once the demo's help you decide whether you like the game itself, your area of interests will likely drive which one(s) you buy; MTO, ETO, Ostfront, or Westwall. CMBN is the "richest" title in that it is the oldest offering and therefore has the most user supplementary scenarios, campaigns, and mods. I find CMFI/GL a remarkably sweet little title with a lot of fun situations to play. CMRT has a very loyal following of aficionado's. CMFB is a natural evolution following CMBN.
Whatever you pick, you can't go wrong. Also be aware that there is a lot of community provided information about these games on Battlefront's own forums (
http://community.battlefront.com/). And don't be afraid to ask anything about the games here at FGM. You will certainly receive copious and diverse thoughts, opinions, and feedback . . . :shocknaz:
Good luck and good gaming!