A very nice tip for killing the first boss: Throw a few points into every air support, put the rest into upgrading your turrets damage, reload speed and accuracy. Also get the flak cannon. The most important bit, however, is to put one point into building armor. This allows you to survive the first bombing run (if no other bombs have hit you), giving you twice the time to use air support. Use all air support at all times against the boss, and he should be easy. Did this on Expert, btw.