Right now the turn-in collectables system is largely worthless. There are collectables used in crafting, and of course the chance for dragonshard fragments, but in general the bulk of the turn-in rewards are just low-value vendor trash.
So my suggestion is you make it possible to turn in most of that stuff for experience points. Not a whole lot, say 1-5, depending on rarity. Say a String of Prayer Beads is worth 1 point and a Fragrant Drowshod is worth 5. This isnt enough to unbalance the game: 10,000 Strings of Prayer Beads are only worth 10,000 experience, meanwhile those rare mushrooms would never be turned in because they're worth about 25-50k plat each.
The idea is to supliment a little experiene here and there. Maybe help reduce the grind a little when you're a third-life TR looking for that last 60k.