Horn of Greed often counts as colorless card draw, but it also gives your opponents some agency to avoid the worst of your wincons
Here's a list along with approximate preorder pricing: Call the Spirit Dragons ($20) Dracogenesis ($20) Stormscale Scion ($20) Teval, Arbiter of Virtue ($10) Shiko, Paragon of the Way ($10) Betor, Kin to All ($10) Neriv, Heart of the Storm ($8) Urnei, the Song Unending ($8) Tarkir: Dragonstorm is filled with many powerful Dragons and Dragon cards worth more than the price of a Play Booster (at least during prerelease)
Yes, unless the card specifically says enchant a creature you control. This is actually a great strategy with cards like Darksteel Mutation to neutralize an opponents threat without letting them recast it
Giant Inheritance will return to its owner's hand from the graveyard only if it's still in the graveyard when its ability resolves
Five rare creatures, each with powerful effects that trigger when they enter and leave the battlefield