Definitely must play Front Mission 3 for tactical-style gameplay. >=D

On the emulation side, it'd a must to try out the Langrisser series, as well as Bahamut Lagoon.

Fans of the infinite amounts of customization in Final Fantasy Tactics will benefit from sampling games like Vagrant Story and Star Ocean 2. Ogre Battle, as well, but you probably already knew that.

As far as finding good prices for Tactic Ogre, I'll tell you your local used game shop (Game Stop, Game Crazy, etc.) will be your best shot, as they usually price at a more reasonable than eBay.