I am curious to know what kind of rope did everyone first use? What material? How thick was it? Length? Color? What did you try doing? How did that work out for you?
I started with common marina and home supply rope, mostly 3/8 inch twisted nylon, though also some 1/2 inch. I bought a lot of 50 foot bags, some I cut to a variety of shorter lengths, others I left as-is. It was all white.

I did harnesses, tied wrists and ankles, spread-eagle, etc. I also used rope attached to leather wrist or ankle restraints. As I progressed, I realized I enjoyed the process of tying and untying my partner more, so I actually prefer doing things slower.

I find 3/8 is too big, and it results in knots which are too bulky

If you could recommend a first rope using those same details, what would you tell someone new to the art?
I recommend synthetic rope, for being easier to clean, doesn’t call for as much treating or maintenance, is stronger, and is significantly less expensive. That said, if you are drawn to natural fiber for whatever reason – smell, appearance, authenticity, photography, even popularity in your local rope groups – I’d say just get what you like.

I suggest people buy a spool of 500 feet, braided nylon, either 1/4 or 5/16 inch. Cut off a few pieces, and then you can adapt the length you like working with.

Have fun! 🙂