if you were to buy 250 grams of KNo3 (potassium nitrate), 100 grams of KH2PO4 (mono potassium phosphate) and 100 grams Trace elements, you would be able to dose for years to come.
I would mix up:
20 grams of Kno3 (3.5 teaspoons)
6 grams of Kh2Po4 (1 teaspoon)
together in 300ml's of distilled water and dose 5ml's every other day, it would give you appropriate nitrate, phosphate and potassium levels.
Trace should be added separately, in it's own mixture:
1/2 a tea spoon into 60 ml's of water and dose 5ml's on the days you don't dose the other nutrients.
All in all dosing should consist off:
Monday: Macros
Tuesday: Micros
Wednesday: Macros
Thursday: Micros
Friday: Macros
Saturday: Micros
Sunday: 50% water change and no dose.
Macros are the main 3 elements (NPK) and the micros are traces.