This may be in the rules somewhere - how many points would you normally use in a game.
For example on a 6x4 table with 1/300 miniatures?
I'll generally pitch the larger of the forces (I always use the scenarios) to be in the 1000-2000 point range. That should get you a game in a couple of hours.
Likewise I use formations rather than points !
It will also depend on the period of the war you're playing; 2000 points of 1940 forces gets you you a lot of (fairly rubbish) stuff, 1944 not so much.
As Ian mentioned probably easier (?) to go with formations rather than points.
It depends on how long a game you want. Also, if you are learning, smaller points are a lot easier to use to get the hang of things. An hour or two game, 1500-2000 pts. All day slug fest with bodies all over the place, 3000-5000 pts.