(sorry if i scatterbrain at times!)
Try the "maximum" songs you can try to do.
What I mean is, what you can just barely pass (or a song you can partially do but screw up at X point, usually the end), spam it. Try not to NF, just spam it. That's how I got "decent" not pro [which I'm not even sure that category exists for ttb (tracktouchpad) yet,] but I know enough to know how to keep breaking forward.
Just know, there are walls you will hit, though this whole year I hit them, a lot, sometimes really hard. But keep a calm mindset and you'll get to where you may want to be eventually. Osu! can be tough when you think you hit the absolute peak you think you can go.
Also breaks. While breaking that "skill wall" is amazing, just make sure you don't break your hand in the process.
If ya hand starts hurting, its okay to call it a day. Don't push it, its not fun.
Speaking of not fun, if you reach a point where you think "I honestly don't think I can do X thing", try to have this mind set "I didn't do that and can't do that, yet". Know your limits, but call it off temporary when you need to so you don't mess up something important. If you get frustrated at times, a osu! hiatus I personally do can help a lot.
As it implies, just don't play osu! for x amount of time, comeback with a (hopefully) clearer mind. Actually that works for anything you are allowed to set aside if you have the time to do it.
Beatmap wise:
https://osu.ppy.sh/s/138369 "I Burn" is what I personally spammed until I could actually pass those level of difficulties. Try "Mao's Hard" first. Don't rush the Insane. Just like everyone's osu! life day one, skipping difficulties is crazy and leads to lots of "Nope". I tried Mao's Hard day 1 when I first joined just to see what 3 stars looks like, needless to say I learned there are some areas you just aren't ready for yet.
Remember to try to have that "yet" mentality I mentioned earlier! Nothing beats doing a year with osu!, and looking back on old replays to see how far you've gotten. (To anyone who thinks they sucked then or now, just note I got a B on the tutorial but when I attempted it with NF a few days after that I got a D. There's progression and there's, "I'm done for now") We all had a "oh god I'm the most garbage player ever" moment. Happens to all of us. Just remember they're only moments, keep going for as long as you can keep that motivation flowing!
If you just want to get just outright raw better at the game (though it's a bit tough to do), spam HR on literally everything. This is the only time I'd recommend NF since HR has no charity if you mess up. But the trade off is your everything is improved but unlike playing normally, HR is really hard to break in. I'm still trying to attempt HR Insanes. I'm not to that point yet. AR 9.5-9.8 is my max, AR 10 is out of the question.
PS: Going on from StephOsu's comment, if we're shinny Pokemon, then does that make the hypothetical-magical girl-mythological being(s) being pro-ttp player(s) shiny legendary(s)?
Hope that helps!
