Use the Feynman method: Richard Feynman was fond of giving the following advice on how to be a genius. You have
to keep a dozen of your favorite problems constantly present in your mind, although by and
large they will lay in a dormant state. Every time
you hear or read a new trick or a new result, test
it against each of your twelve problems to see
whether it helps.
--Gian-Carlo Rota
I regard as quite useless the reading of large treatise of pure analysis: too large a number of methods pass at once before the eyes. It is in the works of applications that one must study them; one judges their ability there and one apprises the manner of making use of them.
--Jospeh-Louis Lagrange (1736-1813)
If there's a book that you want to read, but it hasn't been written yet, then you must write it.
--Toni Morrison
In one sentence, my research interest lies at the crossroads of geometry and physics. Zooming in a bit, I am mostly interested in the interaction of topology with quantum field theories. Other than that I follow Lagrange's advice of learning in the context of a problem. At present, the projects I am working on are related to the following three fields:
My general understanding of mathematics owes to the following classics (thanks to Verma brothers):
Weyl's book was a turning point which pulled me to Mathematics (from Physics). After migrating to divinity for some time, I filled (or have been filling) gaps in my knowledge of Physics using the following (thanks to Anton Zitlin for his semester long course on Geometry and Physics.):
alongside with many lecture notes by Dan Freed (check in particular 'Quantum theory from a geometric viewpoint, Part I') and David Tong. I supplemented the chapters on QFT and supersymmetry from Mirror Symmetry (Hori, et-al) with notes on these topics by David Skinner.
The lecture videos by Kevin Costello on Renormalization and Effective Field Theory is also my favourite (modulo the bad camera work).
I also supplemented Lancaster-Blundell with An Introduction to Quantum Field Theory by George Sterman and What Is a Quantum Field Theory? by Michael Talagrand.
I use this list by Prof. Mikhail Khovanov for the resources and references on Representation Theory. This list is only about online resources and references, so does not contain books like Fulton and Harris, which is my personal favorite.
For people curious about the connection of representation theory to physics, Hermann Weyl's The Theory of Groups and Quantum Mechanics is a great place to look at.
I owe the following list to Sergei Gukov, which I have ordered in increasing order of difficulties.
This lecture notes 'seems' an excellent place to learn about Spectral Networks, in a broad sense.
***Under Construction***
Homotopical and Algebraic QFT by Donald Yau
Lecture notes on 2-dimensional defect TQFT by Nils Carqueville.
One dimensional topological theories with defects: the linear case by Mikhail Khovanov.
Field Theories with defects and the center functor by Davydov, Kong, and Runkel
Cohomological Field Theory Calculations by Rahul Pandharipande
The unbearable lightness of deformation theory by Balazs Szendroi
Operads and Motives in Deformation Quantization by Maxim Kontsevich
*** Under Construction ***