Great guide!
I would like to also point something interesting on advanced / expert level:
Practice deep into one ability when necessary.
While there are a lot of patterns existing in osu!mania with many things to be learned, it's really hard to be a god who is good at everything. Many "ET" (Super expert players) can just play a few styles like god; when they meet styles they are not good at they would just perform like advanced players. I would list a few abilities "ET" hold to perform unbelievable scores. To be honest, each of them needs years of practicing before you get great improvement.
These ability includes:
(1) Single-key rushing

Jackhammers are hard for both beginners and experts. When jackhammers become quick enough to an insane level, it would transform into "one-second killing" period. A typical example is Identity II in O2Jam, where in a special period of song (~3 seconds) you would have to press like 20 times per second on each key to FC it. Since no one can really have such high hand speed, to miss little in order not to let the HP gauge empty becomes the playing target for these songs. If you practice a lot on this ability, you would finally get used to slow (~5 hits per second) jackhammers and are able to a few songs with long period of 20 key per second (KPS).
(2) Sightreading
SV changes are hard, extremely when they come in long period. When you face a 20~30 second of x0.3 SV, it's really hard to catch up the note because of too high density on the board. Try to play a random song with mania speed 1, and you would face the challenge.
If you practice a lot on the ability, finally you would find it easy to read any map, especially on these parts that are full of notes. As a side effect, you would have slightly better judgment. (Some O2Jam ET told me to practice super low speed; They told be you would raise your judgment level quickly but I finally give up on that crazy practice
)
(3) Multi-key rushing

Unlike single key burst, double or triple streams may last for minutes or just the whole song (mostly in BMS songs where they don't use LNs). To have a stable output when smashing your keyboard for minutes, having each note accurately hit and no note wrongly pressed is a really tough task; This need high level of endurance. If you practice a lot on the ability, you would be able to play, you would not only these maps which is full of heavily placed notes, finally you would be able to FC them. (It is really hard for players not having a mistake each 100~200 notes)
(4) Accuracy
Since MAX need really strict timing, getting a song perfect is really hard. when you see your SS score only 990k and are overtaken by 991k S score, won't you be sad? It's a good target to get 999k on each song despite of its difficulty, but is it possible...? (999k is nearly 98% EX Score comparing to LR2, where a lot of ETs have proved difficulties on this task and some of them finally made it on nearly every song.) If you practice a lot on the ability, finally you would found your S overtaken others' SS
(5) Long notes (LN)

Many people love immerse LNs; many people hate it, but the fact is many ET are able to play immerse maps that is already insane difficulty on their un-immerse version. To practice in this style means you would enter a fresh new world, when you find nearly every experience on former play unusable. For many players the typical scene is after years of practice, when they meet the easiest immerse LN maps which un-immerse version is just beginner level they would easily fail. If you can struggle on this and practice a lot on this ability, you would find anything LN easy. Not only on immerse maps, you would found you having no difficulties playing maps with LNs combining with other hard patterns. (Actually immerse LNs are initially designed as a finger practice to normal "hard LN maps".)
As seen in my experience, any one of above abilites needs years of practice to conquer, which make it really hard to get everything good. It's wise to mainly practice one or two abilities when not giving up other abilities, but keep in mind that you would struggle to make progress on this level. Don't worry, any one of these abilities would grant you an honor place on the ranking
I would like to also point something interesting on advanced / expert level:
Practice deep into one ability when necessary.
While there are a lot of patterns existing in osu!mania with many things to be learned, it's really hard to be a god who is good at everything. Many "ET" (Super expert players) can just play a few styles like god; when they meet styles they are not good at they would just perform like advanced players. I would list a few abilities "ET" hold to perform unbelievable scores. To be honest, each of them needs years of practicing before you get great improvement.
These ability includes:
(1) Single-key rushing
Jackhammers are hard for both beginners and experts. When jackhammers become quick enough to an insane level, it would transform into "one-second killing" period. A typical example is Identity II in O2Jam, where in a special period of song (~3 seconds) you would have to press like 20 times per second on each key to FC it. Since no one can really have such high hand speed, to miss little in order not to let the HP gauge empty becomes the playing target for these songs. If you practice a lot on this ability, you would finally get used to slow (~5 hits per second) jackhammers and are able to a few songs with long period of 20 key per second (KPS).
(2) Sightreading
SV changes are hard, extremely when they come in long period. When you face a 20~30 second of x0.3 SV, it's really hard to catch up the note because of too high density on the board. Try to play a random song with mania speed 1, and you would face the challenge.
If you practice a lot on the ability, finally you would find it easy to read any map, especially on these parts that are full of notes. As a side effect, you would have slightly better judgment. (Some O2Jam ET told me to practice super low speed; They told be you would raise your judgment level quickly but I finally give up on that crazy practice

(3) Multi-key rushing
Unlike single key burst, double or triple streams may last for minutes or just the whole song (mostly in BMS songs where they don't use LNs). To have a stable output when smashing your keyboard for minutes, having each note accurately hit and no note wrongly pressed is a really tough task; This need high level of endurance. If you practice a lot on the ability, you would be able to play, you would not only these maps which is full of heavily placed notes, finally you would be able to FC them. (It is really hard for players not having a mistake each 100~200 notes)
(4) Accuracy
Since MAX need really strict timing, getting a song perfect is really hard. when you see your SS score only 990k and are overtaken by 991k S score, won't you be sad? It's a good target to get 999k on each song despite of its difficulty, but is it possible...? (999k is nearly 98% EX Score comparing to LR2, where a lot of ETs have proved difficulties on this task and some of them finally made it on nearly every song.) If you practice a lot on the ability, finally you would found your S overtaken others' SS

(5) Long notes (LN)
Many people love immerse LNs; many people hate it, but the fact is many ET are able to play immerse maps that is already insane difficulty on their un-immerse version. To practice in this style means you would enter a fresh new world, when you find nearly every experience on former play unusable. For many players the typical scene is after years of practice, when they meet the easiest immerse LN maps which un-immerse version is just beginner level they would easily fail. If you can struggle on this and practice a lot on this ability, you would find anything LN easy. Not only on immerse maps, you would found you having no difficulties playing maps with LNs combining with other hard patterns. (Actually immerse LNs are initially designed as a finger practice to normal "hard LN maps".)
As seen in my experience, any one of above abilites needs years of practice to conquer, which make it really hard to get everything good. It's wise to mainly practice one or two abilities when not giving up other abilities, but keep in mind that you would struggle to make progress on this level. Don't worry, any one of these abilities would grant you an honor place on the ranking
