3-5 Common cards
Yes, shadowless cards are worth more than the common Unlimited versions, sometimes several times more for key holos, but they sell for far less than 1st Edition
Getting back all of one's artifacts and enchantments can be a game-changer even if the deck isn't focused on either
Choose any one of the four to play as your commander
Think of the type line as three layers: Supertypes (adjectives): legendary, basic, snow, world, ongoing Card types (nouns): creature, land, artifact, enchantment, instant, sorcery, planeswalker, battle, plus some specialty ones (like kindred, scheme, plane, dungeon, and more) Subtypes (the specific kind): Elf, Equipment, Forest, Aura, Zombie, etc