I have a few possible suggestions for you:
1. If you are talking about the creation of new files, I would recommend creating an Excel template that is pre-formatted the way that you like, and use this to create your new files. Just Google "create excel template in mac" to find instructions on how to do this.
2. If you are talking about opening existing files, I would recommend creating a Macro that format the ActiveSheet the way that you like, and then storing it in your Personal Macro Workbook, so you can run it quickly and easily on any workbook that you like. Note that you can get much of the VBA code you need to do this by turning on your Macro Recorder and recording yourself manually formatting the sheet the way you like.
If you would like it to run automatically, you would instead need to store that VBA code in "Workbook Open" event of the particular workbooks that you would like it to run against. But it would have to be in each file.