Hello this is a great question but is also hard to answer but I'll do my best. The reason it's hard to answer is it's different for everyone and different based on skill level's.
Art Books - First, it's best just to flip through the whole book to see what it's about. When you flip through the book things will jump out at you. If some thing jumps out put a mark on those pages to go back to it later. Once this is done go through the chapters and read the material. Usually there are exercises and you should do them. I find 30 min's to an hour is good enough. Then spend some extra time drawing your own works with those steps from the book for another 30 min's to an hour. This will put what you learned to real world applications in your art.
Studies - Studies is a huge broad terms from everything from anatomy, perspective, environments..ect. So in the broadest terms the idea of a study is to "See" what your drawing. As an example if I asked you to draw an Oak tree with out reference your tree would mostly not look like an Oak but what your mind thinks an Oak looks like. This can also happen with references as well. So the goal is not to draw an Oak tree but that Oak tree from the photo. This goes the same way with any subject matter..
With studies it's best to spend a whole day or even a whole sketchbook on one study. The goal of a study is to put your subject matter into a more refined understanding or closer to master level knowledge.
As for time the simple answer is there is never enough. People who are considered masters of anatomy still do studies and still learn from the anatomy. As for real world application you will find that over time naturally you will become more confident in your art. When you want to draw a character you will draw the character and understand rough spacing for limbs and muscle groups.
As a special tip I will say this. Do not forget to have fun. Studies and such are great but you will learn a lot faster if your having fun. So if you want to get better at drawing hands then draw hands in poses you find to be cool.
Best of luck and I hope that answers your question. Also sorry for the long response but I like to answer fully.