It depends. If you follow Pagano's theory then you should particularly stay away from the 'nightshade' vegetables - tomatoes, white potatoes, tobacco, eggplant etc but also foods that leave an 'acidic' ash in your system such as all meats, most grains etc. He believes you should eat 80% 'alkaline' producing foods which consists of most fruits and vegetables and lots of water. I would say also steer clear of dairy products as some psoriatics react badly to lactose or just have a general reaction to milk and this affects the internal lining of the intestines whihc cannot process milk well in a psoriatic (leaky gut). Also avoid refined sugars and processed foods that are full of chemicals and E numbers.

gluten free grains might be helpful. brown rice pasta is a good pasta alternative.
do you know what makes you breakout?