Assuming a point value of 1500 points (the standard size) a good place to start is a Company HQ, 3 Rifle Platoons, a weapons platoon, and as many Bazookas as you can fit in. Three rifle platoons gives you a large number of troops, which is key if you ever have to attack in a mission. The weapons platoon provides some decent anti-infantry firepower, while the bazookas will protect your men from any tanks that get too close.
You'll probably want to add a battery of artillery; US 105's are great guns and kill anything the enemy throws at you. If you like artillery then buy two batteries.
The other thing you'll need are anti-tank assets. I think your best bet would be 4 or 5 Sherman tanks and a battery of 57mm AT guns. Or, you could try a platoon of Tank Destroyers (M10s are the best), though I think these are too expensive and specialized for a 1500 point game. In larger games they are a great idea, and will kill any tank you opponent deploys. Whatever you do, try to bring at least two units that can kill tanks.
To round out your army, you may want to try air power, or add some anti-aircraft cannon. The 40mm Bofors gun is great for killing airplanes, infantry, and especially light vehicles. A Recon platoon or a platoon of Stuart tanks will give you additional mobility and attacking power.
Hope this helps.