My personal experience after reading tens of thousands of chapters is this.
Realms generally matter and have a set structure that is common throughout the genre.
1) Body Improving Stage - This is when the character first draws in energy into the meridian system(like veins but for Qi) and uses it to widen them to increase the amount of Qi their meridians can hold, or to fundamental improve their body and cleanse out "impurities"(i.e. strengthing bones, washing tendons, toughening skin, etc)
2) Qi Condensation Stage - This is when they open up some kind of space inside their body(usually a the dantian which is just below the navel), which is basically a large storehouse of Qi. At this stage Qi is usually in a gaseous form, and the cultivators can utilize it to use talismans, or buff up weapons, and enhance their bodies. Sometimes they can use special abilities, but often time they aren't able to project power away from their bodies in this realm.
3) Liquid Qi Stage - Basically it's like the previous stage, but the Qi is denser, more powerful, and plenty and they can start using techniques that can project their qi over short distance or have some elemental property.
4) Core Qi Stage - Same as before, just that the Qi has now become a solid core in their dantian. At this stage they often start being able to do crap like fly and use crazy long range powerful attacks.
5) Sea Stage/Inner World - Usually this requires a cultivator to crack their Core which result in it releasing a whole shitload of Qi and greatly expanding how much their dantian can hold. They basically spend a few realms just enlarging this Qi sea until it turns into an entire internal world.
6) Domain/Laws/insights/Intents/Dao - This is kind of more hazy, because it's not unusual for these to show up at any of the previous 4 stages, but the point is that after the whole Qi Sea/Inner world, they usually just continue to accumulate more Qi and the power scaling begins shifting towards how much you understand about certain elemental laws, or your ability to form a domain(A domain being a certain area around you that you have control based on your own dao) that you can control.
This is just the most generic and distilled representation, there are many different types of cultivation levels you can add on, insert, or straight up substitute for.