Very helpful upgrades include bamboo armor for survivability, souldrinker to help regen health in battle, focus: chakra for more skills and revives, and quick attack to help kill mooks faster. Try to save most, if not all, of your silver for permanent upgrades and spend the majority of your xp on your samurai since he's going to do most of the killing, but don't forget to get companions- they serve as great cannon fodder. Hope this helps! :)
Join Ninja Overlords. We're level 2, half way to level 3. Currently 2 members, so looking to expand! Will accept anyone who plays daily or every other day.
http://www.kongregate.com/games/synapticon/tyrant?source=finv&kv_apply=6210003
http://www.kongregate.com/games/synapticon/tyrant?source=finv&kv_apply=6210003 Will accept anybody level 10 or up. currently only 33 fp, but almost 200 loyalty. Leader (me) plays nearly every day two or three times per day.
For everyone looking for a challenge: try using only the first 2 ages to survive for as long as possible. I made it to the final age with just the cavemen on normal.