I would try to avoid pre-mixed soil at department stores. should be good but also could have issues with it too like bug eggs and other bad things. Also more expensive. Get yourself a bale of peat moss 3 cubic feet for around 25 dollars,(ideally) pumice or lava rock. The kind you use for fire pits should work(black or red) the lava rock my store had was called flower rock, ironically =]. the pieces are kind of big and if you have the means to break them up do it, into inch to two-sized pieces instead of handful-sized pieces. But if you can get that pearlie works well too but it will degrade over time. i use both in my mixes. I also use vermiculite but you have to be careful with that because it retains lots of moisture and you don't want to add to much of it. I add my dry amendments(can max specific mixes using veg and flower amendments) to my pearlite and vermiculate to spread it more evenly in the mix. bio char,frass, and worm castings are an excellent addition. A lot of people do not have time to mess around with all this stuff but I guarantee you will get amazing results if you do it right. To me mixing soil is just as fun as growing itself. I used to work for a composting facility that also did vermicomposting (worms). I would stay away from bone meal and blood meal, it is a little too rich and is technically "organic" but does not come for organic sources. It's basically a by product of slaughterhouses and not specifically made for plants. Build-a-soil has great stuff but is expensive, but if you are close to them it might be more affordable. I use giai green stuff which I do believe had some poultry feathers so no exactly the best of the best but seems to work well. also like Dr. Earth and fox farm dry amendments. Also Azomite is awesome IMO. I would get some sort of rock dust in there. and I also add diatomaceous earth for silica. if you want to see I have a few pictures of me making my soil mixes on a few of my diaries.