What kind of deck you're running Aggro decks need to hit the ground running, and they can function with a fairly small mana pool
While it is niche - there needs to be a reason to have this in a Tron or Eldrazi sideboard, for instance - when it's powerful, it's really powerful
If you care about foil treatments, extended art, and showcase frames, collector boosters offer the highest density of premium cards by far
Aerodactyl V 180/196 - Sword & Shield - Lost Origin - Pokmon Extended Artwork Protective Card Display Case
Another way to get new promo cards is to get them from Chansey Wonder Picks, which are a special set of Wonder Picks that consists of cards with a Chansey icon
Borsalino [Alternate Art] OP16-073 (One Piece The Time of Battle | One Piece Cards) prices are based on the historic sales