Hello, thinking of buying my first CNC

Hello

I have been using Fusion 360 and 3d printing for a year now and thinking of trying out CNC for the first time.
I have a project in mind where I will need to 3d mill some clear cast acrylic to a reasonable surface finish so I can polish back to clear. The part is pretty small (20mm dia) and basically a dome. I am thinking of starting out using one of the cheap GBRL 3018 CNC's available with the aim to upgrade in the future.

Any advice of a good CNC from Amazon and the type of milling bit I would need and also what sort of Z height I would get out of these machines with a milling bi fitted.

Stay safe all, Dave