I see I'm too late to this thread! I was going to try to dissuade you since the side missions and equipment choices spiral out of control and the poor challenge pacing of the main story doesn't help. A lot of people on this forum swear by it, though, so it might not be an issue for you.

My advice as you tackle FFTA and others is these games are all about divide and conquer. Move your units so as many of them as possible can burst down a single target all at once. Likewise, position your units so the enemy have as few entry points as possible to attack yours.

If you ever take the plunge on FFT, know completing the game requires you to exploit it's poor gameplay balance.