I also have the same issue as aguther and i tried all your advices so far but non of them worked. From www.mcufriend.com site i found out that the control IC is ST7781 and from below address i found the specific library for the IC.
yet i get this garbled pixals.
If someone can help me it would be great.
I spent this whole week trying to figure out this ?
Download the ST7781 found earlier in this thread.. it worked for one of my LCD's.. i'd suggest that you also open the serial monitor when running the code to see that it actually find the driver and that it - IS - the ST7781
It may well be that it isn't that driver even if it should.. the garbled pixels makes this somewhat obvious it's still a problem with the driver, or that Arduino couldn't make this out by running the code. I have tried so many drivers and libraries out there but what did the trick was to install the latest ADAfruit libraries and - manually - set the driver in the "Graphicstest.ino" sketch that comes with the libraries.
If you load and run the sketch and open the Serial monitor window and see what it gives for an answer when running the code.. If the serial monitor says " Unknown driver" when running the code.. then it's not ST7781...or it couldn't discern it.. in this case try to set this manually and you may as well have a winner
Also: If it is the ST7781, and you have set it manually, but still doesn't work, make sure you have the latest libraries and no doubles of any library. It might be you installed a new library but Arduino still picks the old one.. No doubles - No troubles
Otherwise: Set up the sketch as you normally would before running it and post it here. It's way easier to help by seeing how the code is set up.. maybe there's something you'ver overlooked by trying over and over..