Budgeting is extremly useful both in business and in your personal life. It will give you predictability and control.
If you are looking for something very simple and generic, you can google a local benchmark. In Norway this will typically be SIFO budget referance (calculator).
If you are looking for more details and more control you use your own bank statements for the last three months as your startingpoint. Most online banking has the option to export your transactions to Excel pretty easily. Go through everything you spent money on the last three months and assign each item to a category. One colum per month.
Three months of data will give you a pretty solid benchmark, but keep in mind that some of your cost may be annually og bi-annually. So you may need to make some adjustements.
Once you have sorted out your historic spend per category the fun begins. Now you base you forecast on your historic spend. Typical categories in the screenshot below.
Comment if you need an Excel template!