I'd possibly go ivy, magic garden, Thurston, tablet.

Ivy gives a number of good quests which give her hut (lots of random materials) and the purple cow (chance of gems). Magic garden (when unlocked) gives some items and a chance of the golden apple. Thurston (boxer guy) gives a whole quest line needed for expanding to the bit. Tablet has very rare chance of dropping shards - these have quests with great rewards but are so rare I'd focus on stuff you get rewards for first.