Spirits has many options, even decent budget ones. Ideally, you'd go for CoCo in Bant, and Vial for the other UWx color combinations. You lose Vial and CoCo if you go budget, but you gain more room for answers in return.
Bant gives you ramp for turn 2 Queller and turn 3 CoCo, which is very explosive.
UWx gives you many options, including Curious Obsession, Tallowisp + GosT + Steel of the Godhead, Remand, Cryptic, Favorable Winds, and other jazz.
If you go Esper, even just splashing it will give you access to Lingering Souls, Fatal Push, Zealous Persecution, and even discard if you want to.
If you go Jeskai, you get Lightning Helix, Lightning Bolt, and even Simian Spirit Guide if you want to get spicy.
For a decklist, 4 Mausoleum Wanderer, 3-4 Selfless Spirit, 4 Rattlechains, 4 Supreme Phantom, 4 Spell Queller, and 4 Drogskol Captain are generally considered to be essential. Nebelgast Herald, Remorseful Cleric, Moorland Haunt, and Aether Vial are highly considerable in almost any build.