Every Friday there is a big flea market going on in Agrigento. You can't miss it because in the morning everybody is heading there.
I do not recommend buying jewelry on the market (Mercato) You can find many jewelry stores in Agrigento, especially on the main street in downtown. The main walking street in Agrigento is called: Via Tenea. In the evenings no cars go in there, only pedestrians.
What to buy: I bought things there I never thought I'd buy. For example underwear for my lady and two piece training suits. leather belt, music CDs.
You name it, they'll have it. You can also negotiate with the vendors and if you buy more than one item, they give you a discount.
On the picture I was about 19 years old. Time goes so fast, grrr!
What to pay: $100-
What to buy: Sicily is a land of sun, agriculture, fruits and vegetables. You will find nice cheeses, salami and wines! Especially strong wines, around 12-14°.