You can make your own soil but it requires a few things..
My soil would probably be too much for what you need, but you could adjust the ratios..
Something like..
1 bale of Soil less mix "pro mix, sunshine, nutri plus, there are several. "should have lime in it, if not then its probably just peat and you should add lime"
1 20liter bag of worm castings
8 cups Gaia Green 4-4-4, or any All Purpose Organic Fertilizer. "if using other brands you would check their feeding charts, each brand varies"
1 20 liter bag of mushroom compost
1 20 liter bag of sea compost
1 cup of oyster shells
a dash of greensand "if it's available around you"
a big handful of alfalfa pellets
bat guano "I use this for boron and other nutrients it has in it".. I just eyeball this, toss some in, mix, toss a bit more in "not too much"..
As you transition to flower you would start to add organic flower nutrients, more guano..
This would be a decent mix, you would have to adjust ratios and resources that are available to you.