His hedonism + narcism was a recurring motif. He often indulged in lavish activities and didn't contribute to society. He sold his soul to the devil for the sake of vanity which also calls back to the theme of Faust (selling your soul).
Also the difference between the poor and the rich was another motif (when he killed that girl who worked in the theatre in the East End (poor area) but Dorian lived in the West End (rich area)).
Corruption was another theme.
It's been like 3/4 years since I read it so I don't actually remember that much.
I have, a few years ago. The second half drags like hell, so you can get away with stopping at a certain point (I don't remember exactly but there's a time jump somewhere) and then just reading the end. A good/easy theme to stick with is the function of art and how it reflects on the artist themselves - there's a whole monologue in the very beginning about that, and you can tie in the obvious relationship between DG and the painting in the attic, and the homoerotic undertones between the DG and the painter
