Hi Akos! Welcome to NP and good luck!
Domaining is far from being easy or a get-rich-quick scheme so take your time. Although I'm a total beginner, like you, my only advice to you would be to save yourself the time and money by fighting the temptation of registering/buying few domains at your first days without accumulating enough knowledge to recognize which names will really be a sound investment. Don't despair, though, when you make mistakes, and you will surely make them and continue doing so while sharpening your skills, because truly they are inevitable.