Based on the pauper cube (thepaupercube.com)
Gold slots have signpost uncommons

UW = etb+blink, fliers
UB = control, removal, card draw+selection
UG = tempo, ramp, draw
UR = spells, tempo
RG = aggro beatdown, pump spells
WG = +1/+1 counters, tokens
RW = go wide, tokens, pump spells
RB = sacrifice, tokens, aggro
WB = leech, removal, sacrifice
BG = graveyard, self-mill, recursion