Best Trades for each Villager Profession(Why should you build a Trading Hall)

 A trading hall in Minecraft usually consists of 10 or more villagers. Although some people just use a naturally spawned village for their needs, many(myself included) will promote a proper trading hall with most(if not all) villager profession types. 

So here are the benefits of having all villager types in your trading hall.

List of villager professions

There are a total of 13 villager professions. Each of them have some unique trades that come handy to all sorts of player. Normally most people use Librarian, Farmer, Armorer, Toolsmith and Weaponsmith only, as they are the ones with best trades, but don't underestimate other professions. So first, list of all villager professions(in alphabetic order). 

Best Trades of all the villagers professions

Now that you know how to get all the villager professions, here are the key trades that I find most useful for each professions.

1. Armorer : A master level Armorer trades you full diamond armor, with some nice enchantments if you are lucky enough.
2. Butcher : A butcher may seem waste of food early game as you rely primarily on the meat you obtained from hunting, but you can buy cooked chicken(8 pieces) or cooked porkchop(5 pieces) for 1 emerald from a journeyman(level 2) level butcher. Also, you can sell excess of raw meat items to him for emeralds.
3. Cartographer : You can buy maps for Ocean Monument and Woodland Mansion from him. Ocean monuments may not be that hard to find but Woodland mansion surely is. In all those years of my Minecraft experience, I only found a Mansion twice on my own. Also, you can buy Globe banner pattern from them. 
4. Cleric : You can buy Redstone, Lapis Lazuli, Glowstone and Ender Pearls from them. You can also buy Bottle o'Enchanting from them if you need so quick exp.
5. Farmer : If you have set up an automated Pumpkin/Melon farm, you can get at lot of XP and emerald quickly. Also you can buy the best minecraft food, Golden carrots. Now I know that there are Golden apple and Enchanted golden apple as well, but they are considered God/Supernatural food items as they give you various status effects. 
6. Fisherman : Fishermen are less tempting compared to others. Because if you don't have an afk fishing farm or guardian farm or drowned farm that produce a lot of fish as a byproduct, you won't have much to trade with them. However, they do offer campfire. A great decorative block that eat through you log reserve if you need them in abundance. 
7. Fletcher : You can obtain a lot of emeralds from them by selling sticks. Also you can get Tipped Arrows(eg, arrow of weakness) from them which is useful if you don't have the means for brewing specific lingering potions. 
8. Leatherworker : They also lack tempting trades, the best you get from them is a Saddle, which is not craftable. But, if you're into decoration with Armor Stands, you can get dyed leather armor from them. In java edition, you cannot dye leather armor. 
9. Librarian : You can buy almost any enchantment from them in form of enchanted books, only exception is Soul Speed. Best book to buy from them is Mending, which cannot be obtained from enchanting table. Also, they're the only renewable source of Nametags. On top of that, you can also buy lanterns, glass, compass and clock from them. 
10. Mason : They are one of the cheapest to level up. You can buy Block of Quartz, Quartz pillars and bricks from them. Very useful early game if you are into building Modern Houses. You can also buy Dripstone blocks and Glazed terracotta.
11. Shepherd : Another one with boring trades. Most of the items they offer are fairly easy to acquire in survival. I won't blame you if you wanna skip a Shepherd. 
12. Toolsmith : Diamond Tools(Axe, Hoe, Shovel).
13. Weaponsmith : Diamond Weapons(Axe, Sword).