With all things in life I like to keep things simple.
my local garden centre stocks: sand(sharp), Jack's magic soil, garden lime, bonemeal, fish and blood, chicken shit, Kemp (seawead)
I remove lumps with a garden sieve and add 30% sand,
Add 1/2 cup of bonemeal, blood and bone
Add 1/4 cup of seaweed, chicken shit and lime
Mix for one 18ltr pot
Mix well, soak 2 weeks before using, so all the food breaks down in the soil.
Been using this mix for the last 5 years and I reuse 50% of the old soil.
Very happy the crop considering my dry nutes cost me couple of quick per crop.