Advice for growing in shitty, dry soil

Compost, compost, and more compost. It's like friggin magic, it increases drainage as well as loosens heavy soils, and retains moisture, and adds body to sandy soils.

If it's really dry: dig a big hole - the bigger the better if you are growing monsters, line with plastic and punch your drainage halfway up so it can retain some moisture then fill with medium. Make sure water is accessible or you're fucked either way.

When you are finished with the site clean up your plastic (you weren't going to litter were you?)