Collectible Card Game Headquarters

I've just added a very basic AI mulligan:

If the AI does not have any cards with converted mana cost of 0 in its opening 7 it mulligans once.

This needs some improvements and I want to hear your comments about this. How often should the AI do this? Down to 4? or 3?

A very basic mulligan decision should be more like:

Less than 2 land or more than (numCardInHand - 2)? (Don't count lands that don't produce mana?)
Less than 3 cards with CMC(numLandInHand + 1)?

At least this is what I've been teaching my daughter.

Quality of the cards in hand is relative to the deck being played.

Up to 3 mulligans.

My own personal mulligan strategy works like this:

If land + 1 CC cards >= 1/5, keep hand. Otherwise, pitch it.