Unfortunately, all the data we have for diet and MS is anecdotal. Since MS is such a variable disease, it's hard to say what works and what doesn't!
If you're going to pick a diet, I suggest the Mediterranean diet. It's high in anti-oxidants and the right kinds of fats, and it's good for your brain health.
Basically nuts, dark greens, fish, olive oil and garlic, dark red wine, and chocolate. Stuff we like anyway, right?