Play the game in multi-player offline mode, then advance through all the screens until you get to where you can select weapons. Take as many expensive weapons as possible, but do not put them in your army. After that, select "Back" while holding the weapons to return to the previous screen. Go forward to the screen where you got the weapons, then put the ones you are holding back to where you got them. The points used number will go into negative values and you now have extra points to spend. Repeat this as many times as desired to build your army.