Once your fence and patio are in, you could divide your yard into "rooms". Create planting beds and make pathways to connect them. The slope can be incorporated into the design. Looks like you have room for a vegetable garden, herb garden, flower garden, play area . . . whatever meets your needs. Personally, I'm all about adding trees and shrubs.

Since you're starting with a blank slate, it might be worth a bit of $$$ to hire a professional landscape designer to come up with a plan. Then you can do the work over time as the budget allows. Nurseries often offer this service for very reasonable costs. They can also advise you on soil amendments, irrigation, maintenance, etc. If you're a novice gardener, they can save you a bundle of money by avoiding costly mistakes. Good luck.

Don't know your hardiness zone

https://www.houzz.com/magazine/how-to-site-and-size-a-rain-garden-for-your-landscape-stsetivw-vs~53697312