For a ribbon cut, the Mason Jar/Tobbaco ratio is 4:1. So you would need an 8oz (half pint) jar for 2 ounces of tobacco (50g = 1.75 oz). With a 4:1 ratio you'll need to compress the tobacco down a little bit to fit it in the jar. Likewise 1 pound of tobacco fits nicely in a half gallon (64 oz) Mason Jar.
With respect to other cuts, a pound of cube cut will fill about 75% of 64oz jar and with flakes and coins the ratio is 2:1 where a 4 oz jar will hold 2 oz of tobacco.
I mostly buy bulk and have about 100 pounds of pipe tobacco in various sized mason jars, they are great for storage and ou can find them at any Kmart, Walmart or hardware store. If you get them, make sure to get the wide mouth jars. They are a lot easier to fill and take tobacco out of.