How many excel documents to have?

Hi all,

I'm about to launch my online boutique and I just was facing a little problem with managing the numbers.

To put it simply: How many excel files do you keep for the financial/accounting part of your activity? E.g. Do you keep one separate for all Orders/Inventory/Expenses/Revenue/Forecasts? Or like do you keep mega excel docs with all the info in one file.
Any tips on this would be highly appreciated.

Thank you very much!

Regards.