I would say it would depend on what sort of sound you want to make. If you want rock then you could go:

Big Muff Pi - classic fuzz

Biyang Overdrive - TubeScreamer clone

Vox Wah pedal

Zoom Multieffects Stomp box - MS70 CDR - Great pedal that has Reverb, Delay and Lods of different Modulation(Chorus, Flanger, Phaser, etc).

But the amp and guitar would make a big difference in what pedals you need.