Here’s the proper usage:
Alfisti A group of men or a group of men and women enthusiasts
Alfista One man or one woman enthusiat
Alfiste A group of women enthusiasts
In Italian (and in Spanish and more or less in French), words that end in —ista don’t follow the usual pattern for masculine and feminine forms, so there is no such word as Alfisto in Italian. A man who likes Alfas is an Alfista (al-fees-tah). A woman who likes Alfas is also an Alfista. Alfisti (al-fees-tee) is the plural for a group of male enthusiasts, or a group that contains men and women. The equivalent for an all-female group is Alfiste (al-fees-tay). Maybe this is a picky thing, but it looks silly to use words from other languages if you don’t use them right, in my opinion.