Personally, I'd buy something small that other people sail/race near you.
While I love boats similar to the Lazer, Byte or catamarans like the Hobie 16, or especially the International 505, they are athletic boats.
If you are older and looking for something less "athletic" I'd suggest something where you sit "in" the boat, not "on" it.
Something like a CL16.
https://en.wikipedia.org/wiki/CL_16
She has a main, headsail, and spinnaker so you can get used to what most larger keelboats have for sails. She's unsinkable, and she's got a large cockpit for a a bunch of people. You can even use a trapeze on her.
She's a good size, but small enough that you can really learn about sailing because you can actualy feel how minor changes can affect how the boat sails.
One was sailed from Norway to iceland and some people camp on them with a tent over the boom, some sleeping bags, and a coleman camp stove.
She also has a decent sized racing fleet. At least in Canada.
Racing is a great way to learn, once you know the basics. It also give you a bunch of people with similar interests to hang out with and learn from.
Anything similar to that would make a great small boat which works for beginners, but is also fun once you know how to sail well.