Advice for spelling pitches

Apologies if this is not the right area.

I'm a video game music transcriber, and I have been working on this piece from the 2003 game Castlevania: Aria of Sorrow. It's a small piece, about 21 bars long (the 22nd bar is my addition), but it seems the composer liked to change tonality every bar or two, which makes it a bit difficult to decide on a tonal centre (and thus, a general key signature for the whole piece). Before, I decided on five-flats (B-flat minor) throughout, but that results in quite a few cancelling accidentals. So the way I've currently arranged the key signatures minimises the amount of accidentals necessary, but is of course is still a nightmare to sight read.

Does someone have any advice for the best way to approach the key signatures and accidentals?

Thanks for your help!
- TheWanderingNight