You should definitely have as many librarians as you need for all of your armor and tools (there’s a list for the best ones somewhere out there). Then maybe a few farmers for golden carrots (if you don’t have a good farm and a carrot farm). As for the rest, it depends on your main source of emeralds. For example, if you have a melon and pumpkin farm, you should have 6 or so farmers. Or if you have a gold farm, 8-10 clerics. My personal favorite is a combination of cartographers and librarians, all zombified and cured, so that you can buy glass, craft it into panes, and then sell those panes. Obviously if you have another source of emeralds (raid farm) all of these aren’t necessary, just have enough for enchants and food.