Back when I played it when this was first released, there was no completed English wiki. You are gonna have to do some research if you really want to master the mechanics. There are some great guides on the steam forums for the first game (Venus Blood Frontier). Most of that info regarding combat mechanics will still apply to this game. Frontier actually also has a decent English wiki. For HOLLOW specifically, you can use google translate on the japanese wiki. Also, there is a shitload of discussion and information on this thread that you can read through.
As for your question, bounty hunter gets you ores that you can use to craft equipment. Each instance of the bounty hunter skill gives you an ore of the corresponding rank. Treasure hunter increases rare item drops.
