If you want to do it yourself, or at least give a stab at planning it - the first thing to do is to map out your current space. Go out with a tape measure and a piece of paper - draw everything out, lay out your irrigation and plumbing fixtures, if there are any, lay out your walkways, your entrances, etc.
From there, I'd look at concepts. There are tons of concepts out there in home and garden magazines, pinterest, other home and garden websites. Come up with a few that you like, see if they'd work in your space, what type of changes you'd need to make.
Once you have it laid out - which is the fun part - you can start pricing it up. You can use home depot or lowes pricing for a high estimate, but usually can save a ton if you go to actual landscape companies - especially for buying mulch, landscape rock, and plants. If you plan on doing irrigation, either get a reputable quote from several companies, or price it out from home depot - you probably won't be buying enough to save a lot through an actual irrigation company.
Finally - the hardest part - actually implementing it. If the job is very large, look at hiring a company to do it, or breaking it into bite sized pieces to implement over time. Don't try to start on the entire project at once - you'll never finish.
I'm basically going through this same process right now. I had a concept, bought some material, and have been laying it out and working on it slowly. I'm getting rid of about half my grass in my backyard by extending my patio, adding a walkway and a little sitting area, and then adding a small raised bed garden. My project has become a lot more significant since I've discovered some irrigation piping that needed to be removed, my yard is totally ruined by roots, and it's like 100 degrees every weekend I work on it.
To tie into what
@Gardener said - when people say "low effort" landscaping, you generally have to assume it's mostly just less "watering". Even if you lay down a ton of landscape fabric / weed stop, you're still going to get weeds, you'll still need to re-mulch every 6-12 mo, you'll still need to put down insect control, weed control, etc, you'll still need to add filler rock every so often as things break down. Just recognize that.