You would say De dónde eres? but ive noticed you asked the question in spanish oh well
To dance:
Yo bailo
Tu bailas
El, ella, usted baila
Nosotros bailamos
Vosotros bailais
Ellos bailan
To buy:
Yo compro
Tu compras
El, ella, usted compra
Nosotros compamos
Vosotros comprais
Ellos compran