Pixel art is definitely a balance of real life study and stylization, especially for tiny sprites like these. I'd reccomend doing life studies as well as checking out some existing sprite styles that might be good reference.

I feel like Stardew Valley sprites might be a good place to start since these are pretty similar style-wise. :0

Could do a very slight movement of the shoulders and chest (in addition maybe move/shift the arms just a tad when the breathing happens). I'd definitely play around with timing though since she wouldn't need the breathing animation too often, mayyyybe in between one of the blink cycles.

I'm with Quaesitor, drawing on a grid really helps out. I always use a grid when doing iso stuff. Also i'd start off with square/rectangle shapes, like simple-ikea-ish dressers, fridges, night stands etc. Curvilinear and other complex stuff can be daunting to start out with.

I'd definitely take a look at existing iso stuff to get an impression of how other artists might tackle iso stuff. 

When you feel comfortable, you could post some screenshots of your iso stuff, i'd be down with doing a drawover if you need help. 

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