If you can afford it get some Plant Sucess granular and put in your buckets.....Kinda like what I was using in that Sensi Star grow. I'm a KISS type guy and keep it simple. Everybody's does things a little different. I've tried several yrs to built a compost area from old soil. I don't use it, I could give you a cheaper soil mix, or soiless. Mix regular potting soil into Promix, or just use Promix and fed the heck outta it. There's millions of ways not to complex things and have beauty plants!!! Good luck on your choice, tried and true is hard to go against