You don't actually need weapons and schools in this game. Your survivors earn skills by just doing their job incredibly fast. Need more soldiers? Send some civilians with them and they will have a maxed out combat stat in no time.
The only exception are scientists, who need to be trained in schools, because they gain skill points very slowly.
The hardest part of the game is that it is hard to see for which row the numbers are on large maps. It would be nice if the came could illuminate the numbers of the current row.
How to win the hardest difficulty: Don't give your ships the attack order. Focusing your fire on one enemy ship seems obvious, but it will make you loose. Instead just focus on staying in the best formation.
Specialist levels seem to be completely pointless, except the archer specialization, who is, fittingly enough, the only advanced unit not completely pointless.
There are not enough maps to get experience.
I mean, the cut out spell is almost mandatory, because it is a fast way to get gold. You also need to upgrade meteor to deal with ninja bosses. Of course you need to also upgrade mana pool. That means you need level 14, before you can upgrade what you want and by that time, the game is almost over.