Some hints: Max out Hornet first, you will get 1000 plasma for it. Wasp and Hornet hulls are the best (IMO). Lamp and Bull will carry you for awhile until you get the top gear or enough upgrades. Resistance reduces (if not completely negates) damage from simple drilling of rock. Green planet is better source of material where as Red is better for everything else. You can run into mines before they explode.
Some help for beating the game:
Mp Regen and Hp Regen will get your throught most floors
It actually is worth it to butcher entire floors. (Every floor in fact)
If you can't clear the whole floor it is probably time to retreat.
The only spells you usually need is revealer, heal, and transmute
There is no store on floor 50. (ever)
Wisps are possibly the deadliest enemy (other than the final boss)
If you can't make it to floor 80, go back to floor 1 and save up potions
Just completed the campaign. Hints: It is almost always more efficient to use battle harvesters on locust swarms (with enough weapon and capacity upgrades you will actually gain biomass). In the harder stages, it is sometimes better to harvest a planet completely empty once it lifeforms reach the level 3 (the level before they start fighting back). Blackholes are a good way to build up a planet so that you can attack and get tech points.
Forget Sage, the Riffs, the guy from Last Stand, the ZPCI, and anyone else who claims to be able handle your zombie problems. Just hire these farmers to do the job for you. Really, just sit back and watch the town of them "go to town" on any thing even remotely undead.