Still to many variables I'm afraid.
I don't know what the average weight is for soil, but if you get 0.5/1gpw then you've done well, if it's your 1st grow just getting through it with bud to smoke is a success, it's a cliché but there really is no substitute for experience, every grow you do will improve time after time
I'd expect most the members that can grow a gpw+ consistently have been growing a few years+?
There's plenty of members here that will help you through your grow I can't I don't use soil.