Rehabilitating very a poor plot

I've never purposefully grown anything here, and I'm looking to restore it. I am more concerned about functionality than aesthetics. I just want to be able to grow some native plants for insects and birds to enjoy, I don't care if it's well-groomed.

My current thinking is:

  • Rake the soil to remove years of dispersed gravel rocks
  • Add cheap topsoil all over the yard for more organic matter
  • Plant ground-cover to stop erosion and moisture loss
  • Plant some wildflowers and shrubs around the perimeter of the yard

Some questions:

  1. What to do with the leaf-litter? Should I leave it to assimilate into the soil? Should I pick it up and put it back on top after I add topsoil? Should I bury it underneath the new topsoil? Has it served its purpose and should I just get rid of it?
  2. Is adding a bunch of topsoil going to be enough to grow native wildflowers, or will I need to add fertilizer, calcium, etc.?
  3. Any recommendation for ground-cover that will quickly take hold and save me from any more erosion from Spring thunderstorms?
  4. Is it too late to plant? The last frost was probably 1.5 weeks ago.
  5. Any other suggestions or corrections?

I am a complete beginner, I will take any feedback you have.

Slight slope, lots of erosion from vicious cycle of grass loss, slightly acidic/neutral, very little direct sunlight