your recipe could use a few ingredients ,
peat/coco 1/3
any ratio you want
compost/castinging 1/3
any ratio you want
perlite/vermiculite 1/3
80% 20%
then you can add ingredients , your usually safe at 1/3cup /cu ft soil
people try to balance amendment numbers overall to be roughly equal
or if you want a veg soil 3-2-1
flower soil 1-2-3
think about the ph of each ingredient you add and either test your soil ph (lots of guides online), or try to guess how much oyster shell flower you need,