Have you tried the 50/20/30 rule? Take your take home pay, after taxes. 50% is for fixed monthly cost that do not vary much from month to month like rent, mortgage, car payment, etc.
20% is for important payments or contributions that will help you secure your financial foundation such as paying down credit card debt, saving for retirement, building an emergency fund & also for financial goals like a down payment on a new home.
30% is for flexible spending. These are day-to-day expenses that can vary from month to month, like eating out, groceries, shopping, hobbies, entertainment, or gas.
I hope this helps.