Two males, two females, or one of each?
A same-sex pair is best and it doesn’t matter whether you get two males or two females. If you are intent on breeding, there is much research to be done before undertaking that endeavor.
If you intend to adopt a male and then have him neutered, that is a VERY bad idea. Spaying or neutering of chinchillas should only be done in an emergency situation to save a chinchilla’s life.
Some people believe that animals need to experience motherhood at least once but that is certainly not the case, especially with chinchillas. They are much happier and healthier if kept in same-sex pairs. The females tend to be more aggressive in a breeding pair and we’ve helped people deal with cases where the female wouldn’t let the male eat or rest and the poor male was miserable until the pair was separated.