There are many players online, but most of them are "veterans" of the games series and play in pre-made teams. You will be able to join a game, but don't expect to win any time soon
I would not call MoW a new player friendly game even in SP, and MP is pretty hardcore. If you have some friends to play with - thats the best place to start.
Do not buy new maps until you are 100% sure that MP is what you want to play. I bought all the games since Soldiers: Heroes of World War II came out, and i enjoy single player more then multi-player by far.
SP maps can be replayed 100 times, and they are still fun, since the outcome of each game is so random.
Game editor is very powerful, but you will need to read some tutorials before you start.
I really hope that you will not be discouraged by my reply
Men Of War is THE best WW2 RTS on the market, nothing stands close to it. There are lots of great mods, and a very helpful community!
I suggest you to visit official forum, and read some articles there:
FORUM
Good luck and see you on the battlefield