Honestly campo de fiori is just overpriced tourist theater while testaccio is where actual romans shop for food the price difference is criminal we're talking €4.80/kg for tomatoes at campo vs €1.90/kg at testaccio same goes for mozzarella di bufala €16/kg vs €11/kg you'll save serious money

Testaccio market is at via benjamin franklin near piramide metro station the vendors actually know their stuff and will teach you how to select proper pecorino or tell you which artichokes are best for carciofi alla romana the trapizzino stall inside does these incredible pizza dough pockets stuffed with traditional dishes like chicken cacciatore or oxtail stew trust me it's like street food but elevated

Campo de fiori looks instagram pretty but the quality is garbage half those vendors don't even know what they're selling testaccio opens 6am monday to saturday take metro line b to piramide then walk 8 minutes down via marmorata go in the morning when everything is fresh and romans are doing their daily shopping honestly this is where you taste the difference between tourist rome and real rome