Answer : It depends on what you want your backyard to look like. If you want a patio or deck, those require professional installation. If you're simply looking to make your backyard look nicer, there are plenty of things you can do yourself with a little research.
One option is to add plants and trees. You can also add mulch, stones, or other landscaping elements. Or consider adding a playset, a firepit, or some other feature. With a little creativity and some online research, you can probably come up with some ideas that will work for your backyard and your budget.