I think the best start would be NPC templates, I often use them for showcasing as they are both simple in structure and popular in pageviews. We have a template per game: w:c:tes:Template:SkyrimNPCs, w:c:tes:Template:OblivionNPCs, w:c:tes:Template:MorrowindNPCs and w:c:tes:Template:OnlineNPCs. All of these are nearly identical and could benefit from some kind of inheritance system, perhaps some kind of master NPC-template (if possible). When I designed the templates a few years back I tried to make an as good as possible split between table structure and the 'look and feel'. The corresponding stylesheets are located at w:c:tes:MediaWiki:Common.css/infobox.css and cover all templates across the wiki.
From there on we could probably tackle the location templates (there are way too many of them around, someone made an awful lot of duplicates a while ago and I'm about to propose we merge them back into one location template per game). The location templates are like the NPC templates in structure.
Finally there are the item, books and shouts templates. Those are the more sophisticated ones where we rely on alternative table lay-outs and scripts running inside the tables. I was planning on replacing some of these scripts with Lua versions, but so far I haven't been able to get these working. How do the new infoboxes interact with embedded scripts? Something like the DragonScript template has become a big dependency for the wiki itself over the past years.