I learnt that piece during my first year at uni. It was one of these few pieces which suited me right away despite being very hard. I was truly excited about performing it. I studied Chopin influences over Scriabin music a lot (that was my master thesis about) and according to my studies opuses around 28 are kind of break-through where Scriabin started to develop more of his own language.
Regarding tips - study melodies, be able to transpose them, improvise on them etc. You need to truly know them by heart, not only by fingers. Study harmonies, look for patterns there. And get a good comfortable fingering for these arpeggios on last two pages - it might be not an obvious one, I remember I was actually using similar approach as to the famous C Eb A Eb arpeggio in Etude 10/1 by Chopin for pianists with small hands. So I was starting some arpeggios in Fantasy from 2nd finger instead of 1st if remember correctly. The hardest section for me was the one with the wide passages in left hand before piu vivo in B major, it was hard harmonically and quite uncomfortable. I managed to play this piece with my octave reach, so don't worry about hand size too much, even if at the beginning it is a bit awkward.
Topic: Scriabin's fantasy in b minor