Unless you have a strong art preference, it's best to save your mythic wildcards for cards that don't have a lower-rarity version
I bowed back, my inner 12-year-old beaming
By playing a small number of lands that can add your third color, you can add powerful cards that fall outside of your main two colors
The cream of the crop, though, is the Enchanted Rare variant of Belle, Strange but Special, which features borderless artwork of the Disney heroine in her iconic yellow ballroom dress whizzing across library bookshelves on a ladder, books and papers flying everywhere
For removal, we have Beast Within as an obvious include, but the rest I tried to keep synergistic in one way or another: Smell Fear proliferates our Sagas, Seal of Primordium sacrifices itself so we can reuse it, and Cankerbloom does both