Hi Marcel Riccelli,
I started with a Behringer Neutron before I went into Eurorack and the Neutron thought me a lot, it allows some basic patching and has everything to get started. Budget-wise the Neutron is very reasonable, in Europe it's at about Euro 299. Or you can consider the Behringer Model-D, I don't have experience with that one yet but it's on my wish list. I think to start with, the Neutron is really not a bad choice.
Once you know the Neutron in and out and you are happy with patching it, then, and only then, you should consider to move to Eurorack. Start then with planning a new rack with the buildup experience you got from the Neutron and keep checking this forum of course :-) Please also follow up the advice of Ronin1973 to practice in VCV as well before spending tons of money into Eurorack ;-)
Good luck and kind regards,
Garfield Modular.
For review reports of Eurorack modules, please refer to https://garfieldmodular.net/ for PDF formatted downloads