If you look for the keywords (3russian Foreign Policy") in Google Scholar, you'd find much litterature on the subject that can largely respond to your question.
As an appetizer, and knowing that I am no Russia expert, I'd suggest to read Kennan's Long Telegramme (it is from Cold War but much applies today) :
I recommend reading the The Concept of the Foreign Policy of the Russian Federation because the texts also help us to understand a little more about Russia's foreign policy, especially from 2000-now.
Russian Foreign Policy in the 21st Century by R. Kanet is also a good read because it provides a very interesting overview of Russian foreign policy, its characteristics and its relationship with its neighbours.
If you want to understand a little more the view of the Russians on the subject, I suggest the texts of the Magazine Russia in Global Affairs https://eng.globalaffairs.ru/ which brings good texts on Russian foreign policy, International relations and the world today .
Andrei Tsygankov's books are also great, he has one from 2006 on Russian foreign policy that can help you. Also, there are some texts by Dmitri Trenin that might be interesting.