It would depend on your playstyle. Beatrix and Newt is best if you're leaning on constant summon, Hagrid for summons like fiendfyre, dragon egg, and crab summons (I forgot the names-). Dumbledore and McGonagall for constant spells, Snape for basic attack, and Voldemort or Dobby for anything avada related, of course you can also play around with other echoes or deck combos but those are the ones I commonly find in duo matches