Non-official cards are not allowed in competitive play
Mono red decks will have a hard time setting up for this combo, as they dont have reliable ways to find the pieces, but if you add blue or black, tutors like Trinket Mage and Vampiric Tutor can help you assemble the pieces without slowing you down, ensuring you are able to keep up with early mana rocks and ramp spells with ease
Remember one of the alternatives to MTGA is Magic Online where you do buy cards, but that comparison is its own discussion
When one of your non-decayed Zombies dies, you make a 2/2 Zombie token with decayed, and at the beginning of your end step you may sacrifice a Zombie to draw a card
Faithless Looting is still played as one of the best draw spells in Commander and Legacy nowadays, enabling graveyard decks and keeping the engine rolling
From premier sets to various Universes Beyond designs, there are tons of different themes that Secret Lairs can focus on