Here is the list of all 98 Hobbits/Lord of the Rings Characters in the game:
NOTE: Completing more side quests is needed in finding the other characters. The DLC characters do not count towards the achievement.
You need to buy all the custom character pants, heads, and bodies; such as the whole costume of a chicken or dragon. The character customization is located in Lake-Town.
It is needed to customize an Orc or Horse in Beorn's Homestead for the achievement.
Jimli The Blacksmith – 50,000 studs. LAST FINAL CHARACTER YOU GET! He is the blacksmith always standing next you making forge items. After you get forge all Mithril items and collect all Mithrils you can, then buy him.
42 Characters unlock after completing the Story, the other 56 are unlocked characters you'll have to find them in the hub world.
Locations to buy characters: No locations to buy characters in this game. Instead, you must find them walking around in areas of the world, by exploring this Middle-earth open world hub. Press then go to your map then see where each are located, some unlocked after completing a chapter.
The good thing about this game is it creates a way point to that character to go find them. To do this press on map where you highlight the character with your Magnify Glass. Then press on them to buy them, sometimes you have to hit them a few times. They show up on your mini map and game map when you are near one.