Backyard Slope

We moved into our current home in December. The house is on a slope and the prior owners did a lot of work to clear the yard to make it usable but left it pretty much a blank slate. Our first priority is to work on the hill in the backyard (rough dimensions 22ft x 30 ft) in order to prevent erosion with the fall/winter rains. We'd like native CA plants and pollinators and ground cover, and to use the existing deck - maybe an archway to prevent sitting in direct sun. With regards to timing, we'd like to have things planted no later than Sept/Oct. Our budget is also flexible: $5-10k.