You're thinking in the right direction in terms of having infrastructure support during your first multi-day hike. My first was the Laugavegur trail in Iceland a few years ago, and it helped tremendously that I was staying in huts each night and not camping, both because of the weight, and also because the screwups my first-time self made in what I packed were lessened by the fact I had a roof over my head each night, a place to cook my food, and other strangers in my "cohort" I got to know over the course of the 4 nights who had started at the same time to share advice.

So, hut supported, you could try the Iceland trail, the Kungsleden in Sweden is moderate difficulty and the huts are wonderful, the huts in the U.S. on segments of the Appalachian trail are quite nice (and they even cook you dinner at some!) and there are a few others you can search for. Then once you've picked a specific hike, quite a few people write about their experiences on that particular trail and you can hone in on the specific equipment you'll need to bring.

My biggest piece of advice: be absolutely ruthless about the stuff you decide to bring so you can keep your pack as light as possible for that first multi-day hike. A bunch of extra clothes? No. The very low probability emergency situation that your hut won't have working gas so you have to bring your own stove? No. etc. etc.