Briefly, I''ve been designing a CCG for a while now and have even designed a few of the cards. I''ve got 6 kinds of cards:Action, Upgrades, Units, Personalities, Mainframes (like the King in Chess, must have 1), and Structures. Then I have several different categories that individual cards fall under (still deciding which to use). My question is, approximately how many cards would be enough for a Alpha Set? Any suggestions?

I think 100-300 is enough.
In fact 300 is probably a bit too much...

Decide what cards are used in which ratios and work from there.

If you want Action cards to be twice as common as Upgrades, and just as many Units as Personalities as Actions, and 1.5 as many Structures, map it out:

Having 60 Actions would mean:
30 Upgrades
60 Units
60 Personalities
90 Structures
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300 cards