Every faction in Assassin's Creed: Revelations appears to have a few sets of challenges associated with them. Under some of them it appears there is a reward for completing an entire set. However, I'm having a tough time determining which rewards are actually useful. For instance, one of the bomb maker challenges gives me bomb ingredients at my hideouts, but I have no idea how many ingredients, how fast they respawn, and if they are "rare" or "common" variants.
Is there a list of the challenge rewards, and approximately how useful they end up being? I'd rather not farm a bunch of these challenges if they make very little difference to the game. However, if having one of these rewards early makes certain missions or facets of the game simpler, I'd like to prioritize it.