Garden Setup on a Grade

Hello all. This is my first post after a year of lurking on here! I am working on deciding how to set up my first in ground garden on the property I bought about a year ago. Last year I did some raised beds but this year I want to prepare some land for sowing in ground next year, going for a no till strategy.

I have a picture of the first space that I want to plant. In the future I was hoping to use this space for a high tunnel or a green house so I would like to plan as if I was going to install one. I have two problems, first the space is fairly small, about 20 ft by 100 ft (excluding the existing french drain structure). Secondly, its not flat, I'd bet there's about a 2.5 ft grade there. I was planning on flattening out this plot by adding soil and putting in a retaining wall at the edge of the driveway (not pictured). Is it worth the effort to do that here or should I make different plans? I'm fairly new to this so any advice would be appreciated! Please see the attached picture of the area!

A non level high tunnel will make the construction workers shudder, but will work just fine.  In fact, longitudinal slope is handy for drainage of the greenhouse.

If you add dirt to level it, make sure not to cover all your topsoil with subsoil if you plan on growing in the ground.  Are you planning on heating the greenhouse? Depending on where youre located, a heated greenhouse is more or less cost effective.

20x 100 is a monster greenhouse for a non commercial setup.  

The slope won't hurt your garden so i wouldn't worry about fixing it until your ready to build