Fortunato seems like he is someone that likes to get drunk. He has a lot of money and he seems to enjoy spending it on his own enjoyment. He is wearing a jester's costume when Montresor encounters him on the street. Some people generally choose costumes that represents what they think of themselves, how they would like others to perceive them, and/or what they would like to be thought of as a very funny guy, but he is the kind of "funny guy" who likes to inflict pain and could careless about how the person feels. Many of the "injuries" Montresor suffered from Fortunato may have been painful digs that hurt his pride. Montresor describes Fortunato as "a man to be respected and even feared."
Fortunato happens to have somewhat trust towards Montresor. He approaches Montresor with excessive warmth as if they have been friends for a very long time. His clothing seems to reveal his trusting but foolish nature. Fortunato also referred to Montresor as his "friend" since he have known that it was not a good idea to be alone with a masked man in a catacomb. Fortunate made a huge mistake by trusting Montresor which leads him to his death.
The way Fortunato responds to the situation, makes him be presented as a naive person. He easily falls into Montresor's plan. Since he believes he is the best wine tester and there is no one else like him. So, he wont lose to this person called luchresi.