For instance, if Eerie Ultimatum is your sorcery of choice, then you just need a graveyard deck (maybe a sacrifice-based one?) and a full graveyard to take advantage of it
When that ability resolves, you may cast the exiled card for its madness cost
Timeless is MTG Arenas largest Constructed format where every card is legal
Once youve established your curve and battlefield, you can swing quickly and effectively with the next creatures you cast
The Battle for Zendikar lands are more or less worthless, selling for somewhere between $0.25 and $0.50, but I expect that you'll have a hard time getting much more than $0.10 on buylist once Double Masters floods the market with supply (although they might have some value as trade throw-ins)
For example, let's say you are playing an Abzan deck