Decent strategy: train up a mage and fighter (or maybe a different combination) and gear them up, use the other two slots to train up people. I had a geared rank 30 Sorceress and ran around doing the hardest hunts i could find, was fairly easy to get the monthly fame Req.
Only complaint is how long you have to play to get the upgrades, almost feels like grinding lol. fun game, when you are going the speed of light with a flying turtle the powerups/downs are really hard to even see tho.
fun game, gets old fast and is very hard to lose. also, i'm on wave 20...again. hopefully when you finish it there will be more ship types and slightly higher scaling upgrades. options menu would help fill out the upgrade menu.