Play until you are able to purchase the OGOTO grenade cannon. Purchase it and a good supporting arm weapon on the opposite side. Because almost all missions have a high ammo use quota, you can use the grenade cannon and the secondary gun simultaneously very effectively. Use the arm weapon to kill any small mechs or weak Normals that usually die within a few hits. Use the grenade cannon on clusters of Normals or big targets. By doing this you will never go over ammo quota if you are accurate with your shots and you will complete missions very quickly. The grenade cannon is also extremely effective against the simulator fights. Equip a good generator and low cost boosters, fly into the air, and rain hellfire down on the opposing AC. Their health should diminish quickly, even with high AP. Beware of missile-using ACs, as you are a sitting duck for those in mid-air, unless you have anti-missile shoulder attachments or are able to quick-boost out of the way. this strategy makes a good portion of the game easy, especially missions where you can ignore the bulk of the opposition to annihilate two to four specific targets with your grenade cannon.