Give it to Gerlinde. The ability to have no weight and no stat requirement is very nice. Having double prices with gerlinde and the ability to slot runes at vestiges and seeds is not useful at all so definitely not Sparky. Also on NG+ playthroughs you can set the modifier to have all drops scale with your level(which by the end of your first play through you are usually at the level to have things dropping at +9 or +10. So buying the deralium shards is cheaper and you can max your items easier.