Of course the stonecrafter is going to level much faster than the mason if the stonecrafter is sitting in the workshop cranking out items endlessly, while the mason is getting work only intermittently, and that with a lot of running around in between.
Start with a dining room that has at least one table+throne pair for every four dwarves in the fortress, and at least one coffer, cabinet, door or hatch cover, and coffin for every dwarf in the fortress. You'll also need a defensive wall outside, with roof, and double entrance paths to steer invaders through your traps and traders safely to the depot. After that, and sealing away the surface crop farm plots if you opt to have them, then maybe look into whether the mason needs any special grinding.
Alternatively, make everyone who you don't see an immediate and pressing need for into a mason. Fisherdwarf? Mason. Cheesemaker? Mason. Thresher? You I like, but I don't have my clothing industry ready to use you yet... Mason. Crank out a bunch of blocks and build a mighty defensive wall at least. You'll have a lot of dabbling or novice-ish masons running around, and when a strange mood hits there's a good chance you get a legendary mason out of the deal. Afterward you either disable the mason labor on the masons that suck, or build an extra mason workshop, profile it to only allow the legend to work there, and order all of your future stone furniture through it.