If you're in a deck playing three or more colors, Chromatic Lantern is the perfect addition to your deck
But for others, kidnapping is an option too, as the lore of Homelands teaches us
Voice of VictoryVoice of Victory is by far the best mobilize card: It's cheap to cast, fairly resilient, it gives you the counterspell-pass for your turns, and it also prepares you coffee (it doesn't, but it may as well do)
Shipwreck Dowser Do I need to explain why having creatures that can return spells from your graveyard to your hand is useful in prowess and spellslinger decks
Options include: Mana Crypt, Ancient Tomb, City of Brass, Grand Coliseum, Nomad Stadium, Tarnished Citadel, Mana Vault, Karma, Royal Decree, Ankh of Mishra Mana Crypt is a very affordable $4 online, but the physical copy, eh, not so much ($150)