Of Mushrooms and minerals - the best source of knowledge is the dwarves; yet they do not readily share such lore.
Resources to Gather
There are many resources worthy of search and retrieve actions. Materials one can profit from the sale of, or even use oneself in myriad ways.
Olander's Realistic Systems forms the core of this implementation, but it is much expanded (the fungal side of it is all GM_ODA and Eriniel so sick sick sick stuff).
Musrooms are covered in some small detail here, smithing and minerals are detailed on another page entirely.
All minerals noted in the BOOK OF SMITHING are supported here, and more....
These mushroom routines are all original, so I am at loathe to divulge overmuch here. Let it suffice that the mushrooms are of a staggering variety, running the gamut from harmless nutrition to magically-empowering to straight-up toxic. You eat the mushrooms, you take your chances. Some of the good ones have detrimental effects for those who overuse, some of the dangerous ones have similar (good/interesting) effects if overused.