Spend your $ on your light. Thats the one thing you can’t “fake” or create a work-around for. You don’t need expensive soil. Gooeybreeder has made a life of breeding - growing in 1-2 gallon pots, and using “cheap store bought soil and some cow shit” (according to his Potcast interviews). I keep tubs of soil amended and ready to plant in.
You can build your own soil pretty easily - (/3 peat, 1/3 compost/castings, 1/3 aeration - is a pretty good base). I keep big bags of peat, vermiculite, perlite, and some coarse builders sand. I buy cheap soil and just amend it as needed, and recycle it after I’m done. If it’s too heavy, it gets more aeration. If its mostly peat, add some compost/castings/composted manure. If it clumps up, add some sand/aeration. If it holds too much water, add more aeration. If it dries and cakes quickly, add some vermiculite and a bunch of compost to hold more water. You can make soil “by feel”. It doesn’t have to be an exact ratio.