1-) Use a Nano in Scavenge Mode, when you're going to finish the mission, activate the Nano and you'll have more Fusion Matter. 2-) When you go, for example to level 25 to 26, if you don't finish all the Level 25 missions, finish them and then, do the Level 26 missions. 3-) Do the Guide Missions when you don't have any more World Mission. 4-) Run in a Race inside a Infected Zone to get Fusion Matter 5-) Destroy monsters help you to get Fusion Matter too.
To add to the answer above: When racing, go to Bravo Beach. I figured out a route that takes about 12 minutes and nets you approx. 4500 FM. Avoid going all the way down the second stone slide, as the game will disconnect you when you get near the bottom. 184.108.40.206 18:33, February 8, 2013 (UTC)