That sounds great, and FWIW, I agree, on the right track. I don't always have the same 'stuff' for mulch either, and am not going to go buy bags of it (except as a component of home-made "potting mix.") Whatever comes along, when it comes along... grass from mower bag, leaves of course, trimmings of shrubs, pine needles, kitchen scraps (of fruits/veggies,) newspaper, anything that will decompose will add OM to the sand, silt, clay already there. And you're right, when the water runs out, there's trouble for the plants, and all of the tiny and microscopic critters that live in the soil to make it healthy and alive. Tap water usually has stuff in it that many plants don't like, and who knows how the microbes feel. For sure, nobody is happy about opening their wallet for that.
Digging up grass is really hard work and so many people think it's necessary to start a garden but if they would just do the smother part when they have the gardening urge, simply waiting after that would provide "a bed." And it's so much better 'stuff' than what's left after grass is removed. It was probably not very good 'stuff' where the grass roots were growing, but it was 'the topsoil' of that area. Once removed, the best part is gone, and what's left is less fertile, more compacted, without any life, tilth, humus.
Almost anybody can do it! Not that I have all of the answers, not by a long shot, but I'm happy to help enable, both selflessly and selfishly. If everyone had a beautiful yard, I'd enjoy it more along with everyone else! Sure we need some grass for playing, and mowing around the sides of roads allows people to see so they don't crash their cars due to visibility issues, but I would love to see more mowed areas full of flowers, shrubs, beautiful shade-making trees. Landscaping is expensive and instant. Freescaping happens much more slowly but eventually the results are better, IMVHO.
This pic is from OH, a spot reclaimed from grass about 18 months after starting out.
Here's the back yard from that house, also from '03. This whole back yard was grass the previous spring.
This back yard is from a few years before, different house, also was all grass.
I had a lot more energy back then, and no back injury, so did dig up some of the grass in the 3rd pic, closest to the camera from that angle, but the rest of that yard and the other pics show areas smothered with OM, then I started planting about a month later. (The grass in OH dies a lot more quickly than the stuff here.) Of course adding stuff like finished compost and whatever other OM might become available throughout the year is better, but if nothing is done after 'making' and planting the bed areas but applying a thick cover of the the fall leaves, it should provide a great spot for shrubs, perennials, impulse annuals, even veggies. I grow whatever veggies strike our fancy within beds of other plants. This avoids having pests attacking an isolated monoculture, and keeps things moving around, hopefully avoiding any plant-specific diseases that might stay alive in/on the soil, but, like I said, veggies are not what I focus on, but the ones that are around produce well.
Are you sure the ivy and Vinca can't take root where you are throwing them? There are ways to be sure it is dead before putting in compost, like baking in the sun, or 'stewing' in a bucket of water, encased in a plastic bag (though I try to avoid first-time use of plastic bags for gardening, it would probably take a lot of tiny little shopping bags to contain ivy/Vinca trimmings. IDK how much you are trimming at once. I have plastic tubs I use to contain 'dangerous' trimmings until they are surely dead. Lantana, sweet potatoes, spider plant, don't just die because you trim or dig them up and throw in compost. I wouldn't want to give up that OM so put it in the tubs to die before composting (or using as mulch, in my case.) The more you hate whatever it is, likely because you don't even want it growing anyway, and are kinda irked about the time you had to spend doing that trimming, the more pleasing it is to turn it into compost/mulch. I bring stuff like that home from my Mom's house and DH's Mom's house too. My Mom's agreed to *let* me (after years of near begging) rescue her front yard from an invasion of Vinca that started out as a few plants years ago. Gee, now it's a big job I'll start tackling when it cools off, yay. If I'm going to work and sweat trimming/pulling/digging stuff, that's now MY stuff and I'm definitely (watching DH cart it home in his truck. That's not what my car's for - LOL!) I don't know if I'd be able to make myself do it w/o the prospect of all of that OM I can bring home.
People do come around, Mom asked if she could "have some compost" this spring. If the request had been for something easier, like a kidney or lung, I could of course say yes in a heartbeat. ...but compost? At least she hadn't asked to drive my car, but it was hard to say no to Mom that way - sigh! The last time we drove away with a load of trimmings, she didn't have her usual happy smile. I think she might have been thinking it looked like the start of a "yucky, smelly compost pile" that might be a good thing to have afterall. LOL! (And no, my compost has never been yucky, smelly.)