Theosophy is a fascinating area of occult study, but there are some wildly differing schools of thought, from Donston and his entourage to Eliphas Levi, the Thule society and their association with Dietrich Eckart and hence to the founding of the German nazi party and the countering of their occult leanings by the Occult Bureau under Dennis Wheatley in London.
My favourite character from the whole era, is Austin Spare, the perfecter of so called western siegel magic.

Besant said some nice things about atheism but as her life progressed she drifted away from the secular. All three of these writers lean to Theosophy or notions that have roots in Theosophy. I have never found the ecstatic or individual revelation / intuition to be reliable, so it doesn't interest me.