Something, for example, like the three-mana artifact Crucible of Worlds
Farseek Search your library for a Plains, Island, Swamp, or Mountain card, put it onto the battlefield tapped, then shuffle
I would continue to avoid buying Conspiracy, Modern, or rotating RTR-block cards for another month or so
It's cheap, and quite good, but the power isn't there as much, so it's just hitting at 5, but it's quite good in decks like Spellslinger in Jeskai (built around Whirlwind of Thought), storm, aggro that casts a few spells on your turn like Glorious Anthem and Isamaru, Hound of Konda, control decks with a bunch of instants, flash-matters, and then other key places as well
Then, you can say hello to a formidable free-to-play Blightsteel Colossus on turn 3 or earlier because of Tinkers ability