depends where you live and when ur gunna drive it. If it shows where you are and you plan on driving it in the snow, can't drop it a lot
ditto. if you live in a warm climate with relatively good raods then a 2" drop should be fine. i wouldn't drop it more than that because the celica already has a low stance plus even with good roads there are always speed bumps, steep driveways, etc.
if you plan on adding a body kit in the future you might want to consider getting less of a drop for the same reasons..you're average ground effects kit will drop your car at least an inch