Participate in your cash flow. Know your means. Completely free.
Some of your income and expenses are recurring (rent, paycheck, bills). Enter these in first to calculate your weekly discretionary amount.
Some of your income and expenses are ad hoc. Enter in your ad hoc purchases and bonuses throughout the week.
Always keep an eye on how much you have remaining week to week. It's that simple.
Optionally you can "absorb" bigger expenses or income, to spread them out across multiple weeks.