Starting to do plant ID can seem like daunting task due to the scope of variety in the plant kingdom. I started out by getting a field guild specific to my location so that I could ID what was already growing here. One guide for
trees, one for
wild edibles, one for
mushrooms and one for flowering plants. I take them when I go out for walks on my land and try to ID the things of interest first. It was helpful to know the trees first because then I could narrow down other species of plants by what trees they grow near. Making sure to get out frequently throughout the year and through ALL seasons will make it easier because you see everything at ALL stages of growth. I overlooked a beaked hazelnut hedge row for 2 years until I noticed the nuts just this spring. Then it was easy to ID. Up til then it was just more scrubby junk that needed thinning out. Knowing what grows naturally will help you know what to plant. As I'm sure you'll find out here on Permies, people take weeds seriously, and for good reason. They can tell you all sorts of things about your soil and microclimates. Let them grow and watch them. As an added note, a lot of "weeds" are edible and some make good ground cover for shading soil.
The only other thing I can say is that it takes time to get to know the plant kingdom, so don't be discouraged. I'm no expert but I think I could ID a couple hundred species at least by common name so that's a good start. My 3 year old son can ID about fifty so theres some proof that it's not difficult. Start broadly and then work in from there.
As far as ground covers for the garden, I use a lot of
hay wood shaving for mulch around plants. I've also tried densely planting things and thinning them out as the season goes on.
Example: I plant beets at 1/2in spacing and then harvest every other one as baby/micro greens. After a few more weeks I take out every 3rd one for a salad mix or braising greens. A few weeks later than that, I pull baby beets for salads and pickling. Finally, I pull the large beets as I need them.
I do something similar with potatoes. Planted in rows with increased density as you go down the row. So at one end they are 8 inches apart and at the other end they are 18 inches apart. That way I can harvest from the densely planted side towards the thin side as the season progresses. I get new/baby potatoes first from the dense side and as the weeks roll by the thinly planted side uses up more room to grow large storage potatoes. I've also tried planting quick growing things like greens and lettuces between the thinly planted potatoes so that I can use that space while the potatoes are filling out. By the time the potato needs the space, the greens are harvested.
Ground covers that fix nitrogen help too, so maybe low growing things like clovers and the like would be a nice living mulch if you plant it after other crops have established themselves.
Hope some of that helps.