A raised garden bed

A raised garden bed

Okay I am making a raised garden bed on a slight hill. I will need to flatten the area out and I figured I could just used fill dirt. But I was also wondering about the typical ratio of fill dirt to top soil for my raised bed. It's going to be 20" tall so I know it would be costly to do all top soil but I of course want to ensure fertile soil. Any suggestions? Thanks!
Lots of Pictures,  My first Garden.  :D

Lots of Pictures, My first Garden. :D

Blank Slate

Blank Slate

Gecko and entertainment center pics…

Gecko and entertainment center pics…

Just spreading the Hoya love

Just spreading the Hoya love

Purple passiflora

Purple passiflora

Late July Garden, Zone 7

Late July Garden, Zone 7