Commodities is a tough business hommie. I have traded for 10 years. What are you looking to trade? Eminis, Metals, Energies, Grains,Currencies,Meats...... Futures or Options? I have dealt with them all.
Interactive is about as cheap as it gets, but the markets that they let you trade are limited. As a rule the more you deposit and trade, the lower the commissions.
Man Financial has some O.K. Trading Platforms, but they don't have good risk management software that enables you to see your account P/L until the next day.
Do you have charting software? Are you doing your own trading online or calling your orders in?