Stu, for yeast , go to the big warehouse stores
You can get 2 one pound packages of yeast for about four bucks. They are vacuum packed foil packages. if you keep them, with the tops rolled down tight, in the freezer they last way past their expiration date. If you have a digital scale for the kitchen you can work with "bakers percentages" for bread making. They go like this all of the flour used in the receipe is the basic weight everything else is a percentage of that. Generally liquid is 65 to 73 percent of the weight of the flour, salt? I go to the light side and use 1.2 to 1.6 percent, Sugar, fat, eggs, all depend on the receipe, Yeast two tablespoons full for 5 pounds of flour, That's about twenty cups so for a 6-8 cup of flour receipe a scant tablespoonfull. 6-8 cups of flour will make two loaves.Be careful about adding much flour when you knead the dough, you upset the percentages. If the dough is too sticky cover it with plastic wrap and wait fifteen minutes and go back to it. I work in a 13 quart stainlee steel bowl and use it as a kneading trough. Controls the mess.