Landscaping Hell - I need help

My house sits on a 1/2 acre of gently sloping earth. I have no front yard; but my backyard is huge. When I bought the house back in August last year, the yard was a mess. It was like a tornado came through and honestly I believe one probably did. There was soooo much debris, it was unbelievable.

Here is what it looked like before:

Here is what it looks like now:

As you can see, everything is gone. I had an awesome crew come in last year and they did an amazing job. Yet, now I am left with an almost raw canvas and that is scary. I know that it will take years to create an adequate landscape; but I'd like to start somewhere. Plus, I have absolutely no budget for this, so professional Landscape Designers are out.

Here is one of the steeper slopes next to the garage, I'm thinking I'll need to terrace this to prevent further erosion.

Here is a shot from the very back of my yard, as you can see I have 3 levels.

This is as close to a bird's eye view as I can get. Actually the photo is taken from the 2nd floor bedroom window. That circular shape in the grass is actually the remnants of an above-ground pool the previous owners once had. In the 2nd photo at the top, you can see the timber wall that is built into the landscape along one side of what used to be the pool area. I like that wall and that hardscape is staying.

Any ideas???????