I don't need it, thank you.
'Serve' — 'SER-ve'. Two syllables, stress on first. Open 'e'. Short and final in tone.
Politely declining a vendor's offer when not interested. Much more graceful than 'no' alone. Italian vendors accept it immediately and don't push further.
'Servire' = to serve/to be needed. 'Mi serve' = I need it (it serves me). 'Non mi serve' = I don't need it. This phrase is the polite standard for declining vendors at Italian markets.
Non fa per me.
It's not for me.
Idiomatic — 'non fa per me' is elegant and conclusive
Non cerco questo.
I'm not looking for this.
Explaining that the item isn't what you're after
Non ho bisogno, grazie.
I don't need any, thank you.
Alternative with 'bisogno' — slightly more emphatic
Italian outdoor market vendors are persistent — this is part of the culture, not personal aggression. 'Non mi serve, grazie' + a firm walk-away works every time. Maintaining eye contact while saying it adds authority. Never stop walking when declining.