The two half decks previewed in one of the Magic: The Gathering Foundations Beginner Box are themed around cats and vampires
It's also important to consider what you're trying to ramp into
But on closer inspection, I think the actual most broken card of the year is the reanimation spell Dread Return
Includes deck box, strategy insert, and reference card
This includes dropping the price on Masters set packs back down to $7, reprinting more cards that are expensive because they have a lot of demand (rather than cards like Imperial Recruiter that were expensive because they were low in supply), and refocusing reprint efforts to popular formats like Modern (either by bringing back Modern Masters or by making sure that themed Masters sets are stocked with expensive Modern staples)
One of the easiest places to start is with All is Dust, but a case can also be made for now slotting Hibernation, Riptide, and Wash Out in as well