I’ve been sitting on Tier 2 +11~ for like 5 days now. I do all my dailies, raids, chaos, did all islands, bought all mats from store but failed like 10 times from +10 to +12 even tho success chance is supposed to be like +70 and higher.
Will this get much worse in Tier 3? Because i have no idea if i want to keep up with that…
Just keep playing the game and you will progress. No one forces you to rush. 
Exactly. Many players are stuck in T2 and very few are T3, and thats normal. Its a marathon not a sprint, and tbh being that close to T3 already (9 days since official launch?) Kinda crazy. Slow down, do horizontal content, don’t stress about gear pushing. Enjoy the game and don’t burn yourself out needlessly. You’ll make the upgrade eventually.
If you really want to push for fast progression, the only option I see is to use other characters to farm more mats and funnel them on your main. I don’t know if you’re doing this already though.
With the leftover crystals I’ve had I’ve just been buying Moon’s Breath. For some reason I only need to put two or three in and it’s helped me dramatically.
What’s also helped me, is going through all the islands and gaining more MATS than I acctually lose in total:
Maybe it’s your first rng heavy game. It’s normal, some even fail at 90% succession chance.