My first day of magic training didn't start with a flashy spell or something but instead a lesson of what it is and how it works.
"Magic is divided into three different categories: Personal energies, Universal energies and Dimensional energies.Personal energy is when a person uses his life force for magic.It shortens your lifespan in exchange of power.Universal energy is the energy of the universe in which you are which you can tap into with sufficient training.It is powerful but not at the scale of Dimensional energy.Dimensional Energy is the most powerful one.You can use it if you have an affinity towards a particular Deity's Dimension.For example Vishanti usually grant their powers to the primitive sorcerer of Midgard,Odin derives his power from the Odin Force.Similarly you will find a dimension for yourself in time if you have an affinity.If you want to be a powerful sorcerer you need to always have confidence in yourself otherwise your magic starts to lack in power and believe that anything is possible for you can only wield magic properly if you keep an open mind."
This actually felt quite right to me as Strange became quite a powerful magician so quickly when he started to believe that magic was real,he was already confident about himself and the Ancient One only had to break his mold about science.
"Each and every person's body is different as such they have different, what i like to call,Mana Limit.Mana limit is the amount of mana a person can store in his body without bursting.Each and every spell take a certain amount of mana depending upon your mastery and the extent of the power of the spell.Mana differs on its basis.For those who use Personal Energy the mana is their Life force.For those who use universal energy,mana is the essence of that universe they are in and is all around them.Mana limit applies for the Dimensional Energy,dimensional energy is in another dimension so their are only two ways to use them,either to call forth that energy at the time of spell usage,this adds time to the casting of spell as you have to call for the energy,or you could use your body as a vessel to store this energy beforehand,this reduces the casting time and increases the power of the spell as the energy of that dimension becomes a part of you when its within you thus becoming easier to manipulate.And this is where mana limit is important,for an idiot who wants large amount of power would usually try to store more dimensional energy in his body than his mana limit hence blowing himself up.So keep in mind your mana limit."