I second the advice above. The small box adventurer set adds some fun careers like the iconic rat-catcher. Then the four ruinous power boxes add more on magic, faith, combat and social stuff, with monsters, menaces and an adventure in each. The winds of magic and signs of faith sets have the most value.
the guides and vaults are useful but if less value so if on budget leave off.
Visit glitzman's gallery for useful downloadable like count dimons summary sheets, though I have spotted at least one mistake there in skill section, to liber fanatica for more fan goodness and strike to stun for earlier edition stuff that is useful for background, mad Alfred and winds of chaos sites complete your tour. By now you have detailed maps and calendars and all sorts of goodies.
Ps , we had fun with the signs of faith adventure but I played a bit with it to make it more gothic etc.