This is one of the best articles on soilless mixes I’ve read in a very long time. From adding compost to specific recipes at the home scale, you’ll find this one useful to bookmark and refer to again and again.
The one thing I’ll quote here is the following test procedure. This is critical for any soil/compost mix you make up (and even a few purchased soils I note)
Consider pretesting your potting mix by doing your own greenhouse bioassay. To do a bioassay, grow cress, oats, beans, lettuce, or another fast-growing crop with a high germination rate in your soil mix. If there is a problem with the mix, you will see it in reduced germination or poor seedling growth. You may also compare your new mix to a mix that you are satisfied with.