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
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)
Giant Inheritance will return to its owner's hand from the graveyard only if it's still in the graveyard when its ability resolves
So far, Wizards seems to have put a lot of effort into calculating the value of Secret Lair drops
Horn of Greed often counts as colorless card draw, but it also gives your opponents some agency to avoid the worst of your wincons