Start with 1 big bag bark-based or peat-based potting soil/planting mix.
Dump all of it into a wheelbarrow & use the empty bag to measure:
§ ½ bag ground bark or leaf mold
§ ½ bag compost (yours or store bought) and
§ ½ bag manure - if pots will be outdoors all year
§ ¼ bag sharp sand (‘play’ sand is ok)
§ 1 cup granular garden fertilizer if potting soil has none
§ 1 cup garden lime (not hydrated)
§ Mix all ingredients together well.