l wouldn't use a 3 buckle boot.
lf you can get your hands on a pair of Burton Reactor/Wind/Fire boots l'd say do it. Great boots... loved mine.
lf you're just starting out and not 100% sure if you're going to like it there's no reason to spend big cash. That Prior is 21.5cm wide so even with the longish boot sole Burtons are known for you have lots of room. Great board too, by the way!
Of course, the other option is to peruse the Classifieds here and look for something like a used Head/Deeluxe/UPZ.
Can't go wrong with a Burton 4 buckle boot though, especially if they are really well priced.