YNAB

IMO, You Need A Budget (YNAB) is the best budgeting app. It is cash-based (what you see is what you have) and forces you to assign every single dollar to a budget category. This makes it strongly grounded in reality rather than hopes and wishes. This model heightens the awareness of the spending, reveals the current financial status clearly, and lets you make a good projection and proactively plan for the future.

I think these are all awesome, but this proactive system substantially differs from most other budgeting apps that are focused on expense tracking, and thus it may take some time to internalize this different mindset.

I strongly recommend to spend some time to learn the system until it clicks.