if you use the liquid stuff (api, seachem, aqueon) then it will say on the bottle how much to use. For dry ferts there are a bunch of different methods you could use. i would probably do something like this:
1/8 tsp KNO3 (unless you have high nitrates in your tank than I would use KS204)
1/32 tsp KH2PO4
1/32 tsp trace elements (flourish if you want or csmb+)
I would add all of that into a solution, say 500ml and dose 250ml one week and 250ml the next week (unless you wanna split the above into two, which would be a pain, not sure you can get 1/64 tsp measures lol)
This is based off of EI or estimative index dosing. Do you have a dirted tank (soil etc?).