What functions are you using in Excel that don't transfer?
There are some functions that Numbers doesn't support, mostly around the high-level statistical and financial areas, but all of the common ones should be highly portable, and most income/expense trackers are pretty straighforward at the end of the day.
That said, Excel's approach to spreadsheets is different to Numbers'. Numbers highly favors discrete tables, so I'd err towards one table for all transactions, with separate call-out tables that perform lookups/filters/etc. to categorize, sort, and present the data in a portable way that makes sense.
Everyone's needs are different, though, so there's not likely to be a one-size-fits-all approach.