Need help sorting out greenhouse.

Hi there,

I live in a Northern climate and would like to grow some autoflowers, but I would like to know how much soil I would need and which companion planting to set up. Mostly companion planting for stealth reasons.
So I want to grow a small auto or two, depending on your advice, I have about 7 square meters which roughly translates to 75 square feet (6.56ft height and width x 11,45ft length). And I would like to know which plants I should grow with the autos and how much soil I would need to replace (this part of the garden contains low quality soil) or mix with the original soil. I also have already purchased the full royal guardians seed pack from royal queen seeds.

Thank you for any comments.

I’d just pop the seeds and through them in a 3-5 gallon pot. I have some tomatoes in my GH too. But not to hide anything.
I’ve seen people put geraniums and marigolds to attract predatory beneficial insects