Could someone help me setup Excel as an Expenses Tracker app?

Ok, so I would like to create an Excel worksheet tracking my expenses. While I do know how to create a data validation for a drop-down menu for the expenditure's category (e.g. food, travel etc.), I need help in creating a "formulaic sheet" where if I add on Income it will add accordingly to the balance I had left. I am well aware this is probably not making much sense. ENglish is my second language so please understand.