Purpose/advantages/disadvantages of container ingredients

[tam91]

I personally don't use the self-watering containers, I just grow my tomatoes in 18 gallon tubs. In the past, I've used a mix that worked for me, but isn't generally considered very good I believe (1/3 composted horse manure, 1/3 peat, 1/3 topsoil). I was thinking of modifying my mix some this year. I probably will not be buying the soil-less potting mixes, that's just too expensive for me. So I was wondering, that purpose the various ingredients have, and the advantages and disadvantages of each.

So here's my guesses and some questions - please correct me where I'm wrong.

Topsoil - nutrients for plants. Disadvantage - compacts. Inexpensive

Composted manure - same as topsoil. Additional disadvantage - weeds.

Mushroom compost - same as topsoil, even more nutrient-rich

Peat - nutrients. Holds water. Compacts?

Bark fines - aeration. Does this use up nitrogen though?

Vermiculite - aeration. Kind of expensive

Other ingredients - ?????