Hmm. I read your post now twice, since i am a beginner i am not sure if I could help you on a specific topic, maybe you could provide a little code or pseudo code in your project which explains what you want to achieve what you tried e.g.

What i have learned is that I learn fastest if I got a goal: a project which I want to finish (or others want me to do), learning without a "goal" is not so funny cause you dont see the little progress in your small steps to a given subject.

For sysadmin practice:
I got a rootserver some years back and implemented a Mail Server on it (and other web services) just for learning, i learned so many sysadmin tasks just "by the way" it was -and is- really funny and it is not only theory, so if you could spent some money you could rent a virtual root server for practice e.g.. Or get your own home server, choose a project which you like is important and you learn alot.

Most useful books for me on Linux Sysadmin (I got a shelf of them but those are the most valueable, please check for latest editions):
Evi Nemeth, Linux Systemadministration ISBN 9780131480049
(I like the exercises they are really demanding, my brother was a totally Linux beginner and it helped him at his company too, it must be good if Linus Torvalds himself writes a foreword ;-))
How Linux Works, Brian Ward ISBN 9781593270353
Unix Administration, Aeleen Frisch ISBN 9783897213470
(a little old but the concepts didnt change it is a classic imho...)