What's the best app to track expenses?

Don't go for apps that promise to automate everything without you doing anything - those that sync with your bank and fill everything in automatically often end up outdated or lose transactions. What actually works is choosing something simple that lets you log the expense right away, no hassle.

Wallet or Spendee are good options if you want something lightweight and intuitive. Wallet has this more minimalist vibe, you enter the amount and that's it; Spendee lets you create categories and see graphs without being too heavy. If you prefer something more robust for planning, YNAB (You Need A Budget) is solid, but it costs - the advantage is that it forces you to think about what you're spending, because you have to assign each euro to a goal. There's also GnuCash if you want something open-source and local on your phone, though it's more technical.

The truth is the best app is the one you're actually going to use, because none of them work if they just sit on your phone and you never open them. A lot of people start with something fancy and end up jotting expenses down on paper because the app was a pain to use. So take some time to test the interface before you decide, even if it's just the free version.