Problem is, mutagen and serum will give you random mutations, both positive and negative. Purifier takes away random mutations, both positive and negative. You have equal chances of getting good or bad ones (unless you have robust genetics), so it’s really just a matter of getting lots or very few, unless you want to go to the effort of using purifier and mutagen over and over until you get mostly positive mutations.
Your best bet would probably be to take robust genetics at the start and drink/inject as much mutagen and serum as you can get in hopes that you eventually override the negative mutations with positive ones.