Yes, rarity matters, but a card's financial value is driven by two things: collectability and playability
If you use Helm of the Host, you can triple and quadruple your triggered abilities, which might force you to start using pen and paper to keep track
If there a crease well into the card, youre looking at a 5 or much lower depending on the length
Heres an outline: 10+ removal / interaction 2-3 random creatures 2-3 finishers 4-5 card draw spells 4-6 Grixis Towns Here are a couple example Grixis decks: Reasons to Get Into This Deck Grixis is funny because it isnt a heavily-themed deck
Topdeck manipulation is always fun, and you can do some incredibly powerful things here
Many players think that its enough to be number one simply by having a deck youre comfortable playing, but the sad reality is that most top 1 players most likely abuse the meta and use the best decks in the format every single season