I'll point you her for how to get the game and what version to get:
http://www.coh2.org/news/37043/the-confused-consumer-a-buyer-s-guide-to-coh2
As for the rest:
Ostheer start with 6 Commanders and there are maybe 20 total.
There are 4 ways to get the rest:
1) Sign up for the Relic forums and you can get the Community Defensive Commander (which is terrible)
2) Every so often there is a special event or release that allows one to get a commander. This has happened for two separate commanders
3) Pay money in the in game store. All bar 1 are available that way. I really wouldn't bother at this stage unless you have money to spare, the 6 starting ones are perfectly ok to learn the game with. If later you decide you want to get some more then people can advise you what is good or may fit your style - or wait for free weekend to try stuff out or steam sale to get stuff cheap
4) Warspoils.
This enables you to get everything, every couple of hours or so of gameplay you get a random drop (up to 3 in fact) of Commander, Skin, Faceplate, Bulletin, Skin or Victory Strike. However you get no control over what you get and it might be for a faction you don't play
That is useful info! Now I get it. Thanks.
So, Relic combined F2p model with simple model. Interesting. But maybe its good way. I mean we need game witch will be aliwe for a long time. Look at the RTS now. C&C is dead (killed by EA). World In Conflict? Dead. What else?.. I think CoH series, TW and SCII now is most playing RTS games. And that is all. Also I remember what happened with THQ...
I still hope British Forces will not be last Add-On/DLC for COH2.