That's tough to nail down but I'll try to boil it down too.
The appendix on kundalini from Itzhak Bentov's "Stalking the Wild Pendulum: On the Mechanics of Consciousness" has some key information regarding transcranial magnetic stimulation. Frankly the whole book is wonderful. Bentov's work was cited more often than Robert Monroe was in the CIA's 1983's now-declassified document on paranormal espionage techniques known as "The Gateway Experience". The Monroe Institute is the premier place for learning how to "remote view" which is largely what the Gateway Experience is about so it's kind of something if they're quoting Bentov more than Monroe.
Dr. Joe Dispenza also takes a rather scientific approach to this process of chakra activation. His work is worth checking out: "Becoming Supernatural". He also understands that theta neural oscillations are important just as Bentov figured out.
Theta is so key. Cannot emphasize how important theta is.
The Law of One is really interesting and offers insights into the chakras/energy centers that resonate pretty much exactly with the Hindu teachings in terms of heart/green/love, throat/blue/wisdom, 3rd eye/indigo/full enlightenment. It is free and searchable at
https://www.lawofone.info I can tell you that 49.5 and 49.6 were the first two passages of the Law of One I ever read because they were about kundalini, i.e. chakra activation.
Learning the Tree of Life from Kabbalah is good too, because the central column of the Sephiroth(circles on the Tree of Life) has some 1:! correspondence with the chakras. Kether corresponds with the crown + 3rd eye combined, Da'ath corresponds with the throat chakra, and Tiphareth corresponds with the heart chakra. Yesod and Malkuth sort of cover the lower 3. The root chakra is typically solely associated with Malkuth.
The Tree of Life, in particular Da'ath and Kether, helps one understand the differences between Gnosis and Enlightenment as Da'ath translates to Knowledge and Kether is described many ways, most of which have something to do with light.
I like Imre Vallyon's "Kabbalah Unveiled" for learning Kabbalah. I have some differences of opinion on how far back Tarot goes with the author but he clearly understands that Kabbalah is perennial wisdom that relates to every religious tradition in some way. Imre does a great job of showing all the cross-traditional connections, bridging lingo.