I'm not sure where you are to know the length of your growing season, but you can still grow some this year, and then expand next year.
First, clear a small area. Till it, either by hand, or not.
Buy aged compoast and till it into the soil you already turned.
Choose some already started plants from a nursery, if you want to catch up to the season, or try seeds from things which will still be ready this season.
If you can find nice starts, you can put in a couple of tomatoes, a couple of peppers, a couple of melons, a couple of summer squash, maybe a winter squash and pumpkin. You might also want to try some beans, cucumbers, and eggplants.
Herbs also come as starts. Depending what you like you can try basil, marjoram, sage, and oregano. A nice permanent area would be a good place for rosemary. Break a leaf before buying though, and only buy a plant which you love the smell of. They vary....a lot.
From seeds, with, or without the above, you can put in some green onions/scallions, some pearl onions, parsley, carrots, beets, etc.
Some flowers you can buy starts of, some grow quickly from seed. I assume you want flowers sooner than later.
While everything is growing, spend the early part of summer expanding the garden areas, if you like.
Depending upon where you live, you can plant for winter carrots, collards, kale, mustard, broccoli, cauliflower, cabbage, garlic, etc. Read the packets, which will tell you when they need to be started, and make sure they are a winter variety of the vegetable you choose.
You can also put all, or part, of the garden in cover crops over the winter to improve the soil for next year. Something like Austrian field peas, or a mix of fava beans with vetch, maybe clover. In the spring till them back into the soil.
While your plants are growing, especially with basically unimproved land, dress with compost, and maybe feed with foliar spray of kelp, such as Maxi-crop, and/or a fish based food, such as Neptune Supreme.
Get gloves, simple hand tools, a sprayer for your foliar feeding, make sure a hose....if that's what you use to water....reaches the garden area etc.
That's all that comes to mind right off the bat for a late-start garden. If you have specific questions, though, let us know! :happy_flower