First, you need to decide if you want 3D printing to make things or you want 3D printers s as a hobby. If the former, I recommend at least $600 and preferably $1200 (Prusa Mk3 or Mk4, assembled) as an entry level machine.

That out of the way, there are a lot of kits out there which are fun to build, from models (Millennium Falcon or Rocinante) to sample ICE engines to fun and interesting mechanisms. If you get good with basic design you can print repairs and interesting things that are hard to buy. I’ve made weird stuff like a nut for a Toto flush handle, a customizable collet for pens in a Cricut machine, and a zero-stop for using the Warthog gaming throttle in a space flight sim. None of those are (or were) sold commercially when I designed them.

Printers are useful but ridiculously slow. A day for a single, 15 cm cubed part is not unusual. It’s a lot like building your own Slackware server. There are pre-built versions (unRaid) and a million uses - but if you don’t have one of those uses and aren’t willing to get your hands dirty and your head deep into forums to set things up and/or fix them, it will be a waste of time and money.