I bought this machine about a year ago and it’s been great! https://www.amazon.com/Engraver-Water-cooling-ENGRAVING-MILLING-Engraving/dp/B07XGJZMVW

Had no idea what to expect when I bought it, and there was definitely some troubleshooting at first. There are plenty of good suggestions in this thread, but I wouldn’t immediately rule out the cheap import stuff

Just a standard import 6040, I bought mine off Amazon here.

To gain exposure to the CNC world, how things operate, different softwares and several other things, a 3018 is a somewhat usable gadget, but the spindle just isn't up to anything metal without an upgrade and even then its not very rigid. They're really more a learning tool than a working router. The 3040 would be better for light metals, but is over double the 3018. You really want at least a 500w spindle (weak) but 1KW or more would make you much happier (and actually be useful) if metal is your eventual goal.

For the Amazon desktop CNC's the 6040 is really the best deal (IMHO) as you get the best range of spindle strengths for similar prices to the 3040's with better spindles.

Like this one. A 4 axis 6040 desktop for a grand. How awesome is that? I bought my 3018 a few years ago for over $300 so it kills me how cheap they are getting now.

There are nicer packages for just a little more.

If you want to learn and are short on cash, get the 3018 and then save up for the 6040 cause you'll want it before long at all if you end up getting into it.