What is the absolute minimum parts u need to buy from mazda to do a cheap rebuild of a 13b turbo engine series 4.

 

Assuming your old side housings are not warped or overheated the least amount of parts you need are:
NEW APEX SEALS
NEW ROTOR HOUSINGS
NEW GASKETS

I recommend you put new rotor housings in if you dont want to end up tearing the motor apart again because youre not getting good compression. If side housings are slightly warped i would take it to a machine shop that has the right grinding machine (lapping) to resurface the housings. Mazdatrix charges $50 a face $200.00 for all three. New apex seals is a must!..GOOD LUCK

 

BTW..rotary is not cheap. It will probably cost you more than 1K for the parts i listed above.