What do you want to achieve? Do you want a pretty yard, an Earth-Friendly yard good for wildlife, or something else? Personally, I rather like the idea of a back yard that has so many trees nothing will grow...but that's just my taste. I like the wooded look.

Start out with the things that will take the longest to grow...trees and shrubs. You are probably going to tinker with the bulbs, groundcovers etc. for years, but the best time to plant a tree is yesterday. A baby tree planted in your yard today will be cheaper and have a better root system (making it more resistant to draught and wind) then a five year old trees you buy and plant in your yard in five years. Research native trees and shrubs that birds and pollinators likes, and plant a couple in the front. I'd get someone who knows plants in to look at the baby tree "volunteers" in the back, and mark anything native, edible, or especially pretty you want to keep. Mark anything invasive to get rid of.