Welcome to my Peasant cube!
Currently 455 card singleton
Even Color Distribution (with flexibility for hybrids)
Legal sets include all paper releases from Innistrad onward (Vintage Masters is not legal, for example)
Legal cards include any card that has ever been printed at common or uncommon, and that was printed in one OF those sets (i.e. Serendib Efreet began at uncommon, AND was printed in Eternal Masters, therefore it is legal).
The only current exception to these rules are in the dual lands, which I allow to be of any rarity for the sake of having a healthier format.
Yes, I know that this is a convoluted system for determining legality, but it's MY convoluted system for determining legality!