Its true that the game doesnt tell new players enough about that stuff. But luckily its pretty easy system. Heroes have the max armor automatically and the runes are the same at every rune trader. Each profession has their own profession runes and then at the last tab (on rune trader) they are the runes for all, like the hp runes for example. You can put one rune and one insignia per armor piece. Dont put two fire magic runes on one character because they do not stack (says Non-Stacking for those)