How would I write a formula to calculate the adverage of my monthly expences?

if you were to do this in say, excel, you would create a column for each month. At the bottom (or top if you want to make it easier for quick glance) write a sum function "Sum=(aa##:aa##" where aa is the column and ## is first and last row. Once you have done that for each month, you can add functions to come up with specific averages.

Take the total and divide by # of purchases to see your average cash flow per expense
Take the total and divide by # of days per month to see your dialy average
Add all 12 months and divide by 365 to get average daily expense for the year.