Since I was visiting the club when it was in the Serie A I’m not sure it’s the same in Serie C2. But you should be able to find at least some scarves and maybe shirts to buy outside the stadium.
What to pay: Matchshirt 10 euro
Scarves 5-6 euro
There aren't too many shops in Ancona which is a good thing because therefore there aren't too many tourists either. In Ancona you can find a stinky but worth-to-see market hall with lots of meet, fish and vegetables available.
The clothes shops are medium-sized, like in every italian city, there's also one Benetton-store in Ancona. Terra Nova is a great women clothes shop especially for young women, good quality, not too high prices but trendy clothes!
What to buy: Clothes, food, wine, Finnish dictionaries, Norwegian back packs.. almost everything available!