Whether you enjoy leisurely rides, sportives or dabble in a bit of racing, it’s advisable to have at least 3 rear pockets on your jersey to carry all the requisite necessities for a spin.
If you can find one with a zippered fourth, well that’s a bonus, but it’s not a deal-breaker as most have deep enough pockets to keep things secure.
Some pockets have elastic tops, which are useful if you like to carry a lot of gear. And if you like to have music on your ride, look for jerseys that have earphone ports so you can thread the cable through the inside of the pocket to keep it out of the way.