With these spiritual texts, I'm a broken record: The Bhagavad Gita's ultimate, core philosophy is affecting: We should shed ego in submission to something greater; the book speaks specifically to Krishna, but I think it could mean whatever we define as our purpose(s). It's a tenet that aligns beautifully with The Bible, The Quran, and The Teaching of Buddah.
Like those books, however, there's an underlying sense of secondariness that I simply cannot understand. I can't understand why a benevolent creator is equally egotistical—we're being asked to shed ego in service of the Lord, which seems counterintuitive to me. With that said, Krishna's depiction is a fascinating one; when he demonstrates his celestial, divine form and it's an image too eldritch to comprehend, it's one of the most singularly 'grand' moments in these texts.
Wise stuff at the core with edges that need a little buffering, I think.