I have high interest to professionally know about Euler–Mascheroni constant [I mean more than Wiki page] and to do research on it to develop methods approaching the two unsolved problems about it: Rationality/Irrationality and Algebraic/Transcendental.
I have found no professor in my university (and my city) to help me about this. If I start to study it or to do research on it, I will definitely spend much more on irrelevant subjects than if I had a supervisor.
Would people in here who know about the subject please guide me through the way I have to go?
You can start with a book, for instance: Julian Havil, Gamma: exploring Euler's constant, 2009. It starts at a very elementary level, with a lot of history, but progresses to a lot of results, identities, that are useful to dive into before exploring more technical lands, such as Jeffrey C. Lagarias, Euler's constant: Euler's work and modern developments, 2013.
Apparently, Stefan Krämer, Die Eulersche Konstante $\gamma$ und verwandte Zahlen. Diplomarbeit, 2005, Universität Göttingen is quite cited too, and I could not find an electronic version yet. Yet, he has a webpage on Euler's Constant $\gamma=0.577...$ Its Mathematics and History, a work (German version) with over 300 A4-pages and 1250 items of bibliography. And he says:
For some starting points for rational approximations of irrational numbers, continued fractions and Diophantine approximation: