You get building materials from both the Faerie Exchange and Adventuring to the Plume Hive. I like the exchange since I actually get a consistent amount of each faerie supply (usually one of each: beam, block, and paste). The adventure drops only two random faerie building supplies for me, but I also get energy and have the chance a getting a rare drop (like a faerie campsite). I normally do 2 exchanges for each 1 adventure. Everybody is different and has their own preferences, so you'll find your own niche. Good luck!