well there are a bunch of books/online courses you could try =P
on books theirs the "Successful drawing" by Andrew Loomis (has the 10 basic fundamentals and goes in depth in the theory behind each one of them)
"Theory of comics and sequential art" by Will Eisner (more geared at comic making and storytelling, you can use it for mangas if that's what you like =) [manga = japanese Comics])
and if you have zero money there's actually a guy called uncomfortable in reddit doing a free art-fundamental course on reddit "> r/artfundamentals" or his website drawabox.com (has homework/exercises and challenges to get better at the fundamentals at your own pace of course and is more like a university class/course but by the submission of people who been there for 5 months it seems to work)
these are just the few things I've found to be helpful so if you want to try them be my guest =P
but again this is just my suggestion you can do whatever you want
edit: I've also tried a cintiq since my sister bought one on the cheap side (she got lucky) it ain't that different from my tablet if I'm honest =/
you just got a screen while drawing and it was kind of slippery (compared to my tablet or paper), you also had to be extra careful with it since you would get some of your skin oil on it (need to buy a glove for it I tell ya) but my sis seems to like it so maybe if I played with it more I could give a more in depth analysis for ya XD, though she loves it she has admitted she would never pay full price for it =/ she ain't that rich