If it needs brainstorming then it’s not simple enough. This obsession with bottles is so funny.
Make a decent soil mix from certified organic bagged soil, with some basalt and malted barley. Also mix in and then later topdress with kitchenscraps, dandelion, nettles, tree leaves, grass clippings, kitchenscraps, banana peels.
Sow cover crops too.
Water only.
I only use rainwater or bottled water.
Reusing the same soil. Sowing directly into the same pot.
That’s my idea of simple. And it works for me.