There are four common methods of cultivation, qi/chi, mana, Force, and faith. While World Laws will cause an incredible amount of deviation and different methods to arise, most cultivation methodologies will fall under those categories.
While there are many methods to Ascend, there is only one method that allows Ascension even without cultivation, and that is tapping the power of pure, Undefined Possibility. This is so dangerous and risky, though, that it may as well be suicide. Using this power to reDefine yourself as you wish requires a near impossible Will save, as you would have to do so before becoming entirely unDefined once the process starts happening. There is also additional criteria of being in an area where the edges of Reality are more clearly demarcated as well as being an individual with an external perception capable of viewing and understanding the edges. If any actually succeed, we will use the term Chaotic God to refer to their position, as the results can be mixed.
The other methods of Ascension require cultivation and are far safer in terms of continuing one's existence. Qi cultivation, sometimes called chi cultivation, involves increasing the magic power of one's aegis, or bodily domain. This aegis usually requires a core within the body, with the location varying according to the cultivation method or world Law. There are thresholds for various levels of this aegis as more of the cultivator's existence becomes Defined by his/her Will, though these thresholds are usually Defined by the world's Laws. Most worlds have Laws with punishment clauses for the thresholds, and so inflict Heavenly Tribulations as what was once Defined by the Will of the world becomes Defined by another.
In terms of benefits, qi cultivation allows one to strengthen his Definition, slowing Definition entropy significantly. With the right techniques, cultivation can also alter one's Definition. There are examples of cultivators evolving into aspects of beasts, though these techniques almost always entail cultivating a foreign qi and making it part of you, thus altering the base Definition.
As for the dangers of Qi cultivation, most world Laws require precision when cultivating, and indiscriminate absorption of foreign energies can make one's Definition fuzzy even as it allows him/her to affect the world around in a more significant manner. Definition degradation due to incorrect cultivation techniques are usually referred to as degradations. In either case, meditation and energy circulation is required to firm up one's cultivation base, or to be more precise, firm up one's Definition.
My final point I'd like to bring up is solitary/closed door cultivation versus practical cultivation. Qi is based on one's own self concept. The thing is, other people's views of you affect that. Faith cultivation actually uses others' concept or Definition of another to Ascend. Even more than that, a cultivator will make other people's views part of his Definition. A king is more likely to be able to cultivate a regal aura just due to being treated as royalty all the time. A poor person will be happier than a rich person if the poor person has a smiling and laughing family. This is why some cultivators tend to shun the company of others. They just don't want additional variables in their internal Definition that they are building.
To put it more simply, cultivators who enter closed door meditation do not desire additional changes to their Definition and want to focus on gaining power as quickly as possible to advance their cultivation. Ironically, this will usually make one's Definition fuzzy, making it harder to take the last step over a threshold.
Practical cultivation, where the cultivator interacts with the world and tests his/her limits, is useful to help solidify one's Definition by understanding the limits and usual processes that the cultivator or his/her opponent can reach. It might not always be as efficient as closed door cultivation, but it usually forms a more solid cultivation base (Definition).