Poor Man's SeaChem EQ(PMEQ)
The ratio I've been using is 3:3:1
K2SO4, CaSO4, MgSO4
This will provide a fair amount of K+ relative to Ca/Mg.
Most folks have enough Ca relative to Mg.
What will get folks into trouble in doing their calculations are that these are hydrated forms, Eg
MgSO4 . 7H2O
CaSO4 . 2H2O
You can vary and make your own, but this about close to what SeaChem has.
also sells CaSO4 and PMEQ if you want it.