Ok, make sure you have your proper drivers, or use the Osu! specific drivers for any tablet (I definitely recommend)
Go to the download section to download, and make sure you follow the installation instructions
https://github.com/hawku/TabletDriver
now this next step involves opening osu
uncheck os tabletpc support
uncheck reduce dropped frames, detect performance issues
and im sure you know set your fps to unlimited
make sure your game is fullscreen that kind of stuff
And just to make sure about something,
a while back I updated osu and it started doing this weird thing that made it incredibly hard to play
it changed my setting for universal offset. Make sure that is at 0
open task manager
go to the services tab
Scroll down to TabletInputService
right click and stop
right click again and open services
scroll down to it again in this new window
this time it is named touch keyboard...
right click on it go to properties
change startup type to disabled
IF THE NEW DRIVER DOES NOT SEEM TO BE WORKING, RUN THE .BAT FILE
IF IT CONTINUES TO NOT WORK PROPERLY, MAKE SURE THE MANUFACTURE DRIVER IS NOT RUNNING

set the frame limiter to unlimited
uncheck the following: compatability mode, reduce dropped frames, detect perfromance issues
check fullscreen, and letterboxing
under the detail settings uncheck everything except snaking sliders
set the background dim at 100%
ignore all beatmap skins, and use skin's sound samples
personally I would say uncheck automatic cursor size
Thats it really, the rest if the settings you can play with yourself