You might be surprised, last time i heard, TRD LSD's were fairly cheap but would be one of the last things i'd do. A set of TEIN coilovers would be my first choice.
Also, some gen 6 Celicas (S54 trans) have factory LSD's and can replace the standard S53 in your celica, fairly rare but they are about, could be a cheaper option.
_________________1990 Toyota Celica GTR 4WS ST183
- Steer From The Rear, Literally!