Expenses Query Questions

I'm looking to write 2 queries and am looking for guidance on the correct records and fields to use.

Query 1 - I'd like to identify expense line items less than $25.00 with no receipt attached.  Ideally, I'd like to identify as soon as possible and not after payment.

Query 2 - I'd like to be able query expense items that are sitting in users 'wallets' but are not associated to an expense report.  I anticipate users will accumulate expense items in the wallet but not submit or not submit timely.  I'd like to have visibility to this.

Again, just not sure of the best records and fields to use.