Cultivation is you refining aura and evolving which increases lifespan and strength it's split into tiers and realms.
Tier 0-9 is cannon fodder, you lack the ability to use aura skilfully and you are classified as still mortal all the way until transcendence
After the 9 tiers is the realms each realm is split into nine floors (which are basically small realms in cultivation novels) is Transcendence which is where you temper and transform your body into element(s) of your choice the more elements you choose the stronger you'll be in the future and it be easier for you to advance in cultivation later on.
However the more elements you choose the longer it takes to cultivate and if your not talented enough in a element it may takes decades. Also one you chosen the element(s) you cannot change so you must cultivate or die. After you break through transcendence you experience a tribulation and from now on at each big realm breakthrough there is a tribulation.
After transcendence is the Soul Purging realm where you use the elements that you use to temper your body and temper your soul with them the more elements you used in the transcendence realm the quicker this realm goes. At the end of this realm you form a Soul body which can be used to revive you and it can also leave the body however it is still very vulnerable to the physical world. You can also fly without wind elements or techniques when you reach this realm
After the Soul purging realm is the Enlightenment realm where you use the soul body formed in the Soul Purging realm to feel the physical world in your most vulnerable state cultivating the mind allowing to consolidate your realm and thicken your foundations. Once you reach floor 9 of this realm you once again temper your mind with the chosen elements from the transcendence realm.
After is the Monarch realm where you can teleport by tearing through space with your body however this is still not as fast as someone who can teleport using the space element.
After is the Dao realm Where you cultivate your understanding of elements after you understand laws your elements transform into laws which are stronger than normal elements. You need good comprehension for this and once again the more laws you understand the stronger you are later on.
After you got the saint realm where you fuse your laws into your tempered body, mind and soul creating a body of law, soul of law and Mind of law.
Tribulation realm you go through nine tribulations at each small realm. Each one more dangerous than the last, Each one rebuilding and perfecting you BOL,SOL and MOL
Unity Realm where you merge your body of law, Soul of law and Mind of Law.
The peak is eternal realm where you are immortal for as long as the world exists.
Cultivation techniques and spells, equipment and treasures (medicine)
All of these things are in the same tiers the tiers are
Mortal (tier 1-9)
Transcendent
Soul Purging
Enlightenment
Monarch
Dao
Saint
Triubulation
Unity
Eternal
The higher the tier the higher cultivation or comprehension needed to use the treasure/technique/equipment
Spells are ways of using aura and can be learnt by anyone some spells have different elements needed you can also make your own spells. Simple things like creating a weapon out of an element do not require specific spells as it falls in the category of aura manipulation
A lot of physiques and bloodlines have a specific cultivation technique an are normally imprinted into the mind of the owner once they are ready to cultivate so around age 5 some are ready earlier or later depends on comprehension.