Also look for your local Master Gardeners group or club. MG's are normally a group of local, dedicated, wonderful old lady gardeners, who have decades of extensive training and practical experience with the local flora. My Mom is a Master Gardener and designs gardens for a living. Her gardens ALWAYS work beautifully, while gardens that follow local university guidelines often have major issues. I often see my Mom shake her head at planting an X next to a Y and saying things like, "Oh, you can't ever plant those two together, because the blahblah from the X interacts with the whiggywhiggy from the Y, and turns the soil all acidy. Chases the worms right out of the garden, and your soil goes to hell." Or similar things... MG's also have regular plant sales, and are just the sweetest people.
Good advice, thank you. We definitely want to limit ourselves to just one or two flowers, partly because of the whole interaction issue, but mostly because different plants have different properties and since we're new at this, we don't want to overwhelm ourselves maintenance wise.