A useful crossbody bag should hold the essentials without becoming a portable junk drawer. Before shopping, place the phone, wallet, keys, and any daily must-haves together. That small pile gives you a more honest idea of the capacity you need than a product photo alone.
Look at strap length and orientation as carefully as the compartments. The bag should sit close to the body without pressing into the neck, and it should be comfortable on either shoulder if you plan to wear it for travel. Zippers should be reachable to you but not left wide open behind you in a crowd.
Inside, one or two purposeful sections are often easier than many tiny pockets. Check whether the fabric and hardware suit the weather and level of use you expect. A simple, neutral design can move from errands to casual outings, making it more likely to earn its place in the closet.