Sorcery
Sorcery is among the hardest things one can study. No other school demands so much skill, diligence and time. Sorcery rests on mental concentration, discipline and training. The power you learn to control comes from you and manifests through two basic elements - fire and air.
Acquiring knowledge
Even lower feats and spells are not easy to absorb, but up to about the 3rd feat (and 2nd level spells) these teachings are accessible to the wider public. That doesn't mean anyone will teach magic to any old scoundrel or country lout. Every expert in magic is proud of their art and does not tolerate its misuse or even desecration.
Adepts of magic
Feats of the 4th level (with the condition that you already know 3 feats) and higher can take up to a year to master. They require a lot of theoretical preparation and practice, but also the guidance of an advanced master. Only a few chosen ones, born for magic, can master these practices on their own; the others can only quietly envy them. Moreover, if a feat broadens the student's knowledge so much that it gives them access to all the spells of the school (up to a certain level), their preparation must be much deeper (they must already know many such spells).
Masters of magic
Master feats (6th level) represent the hardest and rarest things that can be learned at all. The preparation itself usually takes up to 10 years and includes studying spells (knowing dozens of spells of the school), general training, knowledge of secret teachings (Exploration of Mysteries), conversations with other masters, reading hundreds of books and scrolls, etc.
In short, this school is not for weak natures who want everything right now and think that magic is just a swift journey to power.
Magic schools and guilds
In some places we can even find real institutions that teach magic, but also control it. This is often in accord with the ruling class, which doesn't want just anyone to gain considerable talent and rob, kill or hypnotize honest inhabitants without restriction. Such institutions have their strict rules, but above all they persecute renegades (even more than in lands where magic is forbidden). Often it need not even be an actual building or a real institution, but just a society of people who know each other well and regulate magic (and also teach their successors).
Dark teachings
Of course there are also faster and freer paths, such as necromancy or consorting with demons. These practices, however, tend to be rooted out by everyone - wizards, priests and secular power alike - because nothing good ever comes of them. On the other hand, it is precisely these individuals who have the fastest path to power, but also to the other world (unless they are careful and clever enough to hide).
If your deeds are dark and destructive, you will moreover draw closer to what wizards call the Darkness. There is also the danger that the Darkness will one day devour you.