Go by the lowest rarity the card ever had. I've got a new, uncommon corrupt in my deck because corrupt used to be common, for example. Same goes for your general: if it was ever uncommon, it's good (e.g. Serra Angel is fine).
Other rule clarifications: only Paul is allowed any colorless nonland cards. Colored artifacts are fine in the deck of that color. As for lands, only lands that produce your color or colorless mana can be used. If it has a colored mana symbol on it that's not your color, it's out. So, we could all use Opal Palace or Command Tower, but only the white deck could use Abandoned Outpost, for example.
And I know some of us are posting our decks on here as we build them, but please don't go looking for hate cards aimed at others' cards to put into your own deck. This is not that serious. Despite this lengthy rules post.