UX: (Optionally) place amount ("how many?") field first
Background
I have an expense in mind, because I just bought something. The most "difficult" thing top remember is the amount spent. This is easy to enter though, I don't need much thinking, I can just read it from my bill, their that away and then enter it in the app ("temporarily" having that saved in my head).
The most difficult thing to imagine is the name I want to give the expense, i.e. the "for what?" part. I often have to think on how I name it, because for a supermarket or so there is no name on the bill. Also I could have a name schema for myself that I like to adhere too. I don't have to remember that though, as I just think and enter it directly.
Proposal
As such IMHO I want to enter the amount of the expense first. It is the thing that is hard to remember and I want to get "out of my head". If I first need to think about the name of the expense I may actually forget the amount of my expense in between.
This has bothered me often when entering data. I would currently need to select the correct input field that is somewhere in the middle.
As such I would like to have that input field first in the form for a new expense. Optimally, you could make this a setting so other users could keep the old order. But that is your decision.
Alternative ideas
Or just make the whole layout configurable, so one can select their own order. That would however likely be more work and you would still want to choose sensible defaults.
Other apps like (name forgot) do it like this.