Custom Villagers

I think you should make a mob with a villager model.

Next make a GUI, see the example of mcreator of the "Fusion table", it can help you to make the trade.

Make a procedure that open the GUI and put it in the event of the mob of "when right click".

I hope its helpful for you.

Make a procedure that only has the [Open GUI for Provided Player, GUI:] brick. Select your custom villager's GUI.

Next on the When Mob Right Clicked option, place that procedure.

In case you didn't know: the When Mob Right Clicked drop down is on the page that you make your mob.

IK this Post Is Old But i Figured out one way of Making Custom Villagers

Using This Reddit post  https://www.reddit.com/r/feedthebeast/comments/cbgxvw/vanilla_villagers…

And This Comand Genorator 

https://www.digminecraft.com/generators/villager_trade_1_17.php

I was able to make this code for The Mod Gr33n's Magica 

I am thinking of adding in a vilager you summon some how by making a procedure run this cmd (on the server side i think)

/summon villager ~ ~1 ~ {VillagerData:{profession:toolsmith,level:5,type:plains},Invulnerable:1,PersistenceRequired:1,Offers:{Recipes:[{buy:{id:"greens_magica:magic_card",Count:64},buyB:{id:"greens_magica:energy_card",Count:64},sell:{id:"greens_magica:smite_curse",Count:1},maxUses:9999999}]}} 

you can add more trades if you want as well

You can actully make villagers trade modded items by using "parentheses"  keep in mind it is case sensitive 

if I am making a villager what "mob natural spawning type" should I put so it spawns in villages

This is very old now there is 'custom villager profession' creator.

hello, still need help?

@sunshineLay_02 i would need help on how to create the gui to be exactly like in normal minecraft but for the trades to be randomized,like in minecraft each villager has different trades and different costs of the items and i want to do that with my custom items