Welcome, Pau. Your course of action is commendable. Many people do things in reverse --- unsuitable machine teamed with even more inferior grinder, supermarket beans and lessons are trial and error.
But by the time you are adept at roasting and grinding, youll know what coffee machine you should be jumping to and thus hopefully eliminating the costly intermediatery upgrade steps.
As far as a popper goes, they are all cheap and similar performers. Spend little on one and if it fails, you wont have lost much.
Youll need a tamper of sorts, some easily gotten for around $25. Scales which will weigh to a gram.
Use the equipment you have or plan to get --- then think about the machine.
Hope this is of some use,