I haven't tried cutting out gluten or dairy though, just cut back on it / trying to cut back on it!
I am sure you know that diets don't work!
A diet implies that you are doing something for a short period of time only.
And just like weight - the psoriasis will return when you stop the diet and return to your normal / old way of eating.
Most people find that any dietary changes are commitments for life - a lifestyle eating plan rather than a diet.
Anyway just thought I would mention that.

The two biggest food problems reported are gluten and dairy.
Both wheat and dairy cause flares in me.....even a smidgen. I had a bit of a session on wheat recently and had psoriasis pop up on my face, which hasn't happened in almost ten years. If I totally avoid certain foods my skin remains free of psoriasis patches, if I stray from the eating plan then the psoriasis flares up.
So to clear psoriasis it tends to require complete 100% avoidance of certain foods, not just cutting down. Of course, you could be different, I am just commenting on my own experiences and others so far.
For example; Lazza - he just cut dairy down and not a lot happened ~ he then started to totally avoid it and as he said he experienced a huge clearing. Whilst all this was going on, he continued to drink the Green Smoothies everyday,
just as I continued with the vegetable juices.
Which brings me to another vital point: its not just what you avoid that is important; it is also what you put in.
I was reading a forum post where they said they had clearance for the first time every after totally avoiding gluten and dairy -
plus something else, can't remember what - whilst drinking daily green smoothies and vegetable juices.
I don't find dietitians particularly useful for anything, so probably best to do your own experimenting and evolve your own diet.
This website has several psoriasis success articles on it: drfuhrman.com/success/SuccessStory.aspx?id=146
His blog also contains some fantastic nutrient rich recipes
Anyway congratulations on taking the first step - as they say, the first step is the hardest.