[Ts4EVER]

Personally I go rather light on the support, especially if I have a company size force. Much of the support I buy (fittingly) with support points, especially artillery and ammunition. That way you get the impression that the force has varying amounts of artillery support for example (as is realistic). I also try to stay away from extremely rare units, like 88mm gun portees or flame thrower tanks in my core force and buy these as support rarely.
I am under the impression that aa is rarely worth the points, certainly not as a core item. When you play against the Americans or early Germans it might be worth buying these as support though.