Its a ticky situation, because the only thing worth it its not avaible on the L2 Store, and that would be anything to help you to even your personal economy.
Let me elaborate:
Right now if you XP normally without any XP boots, you will level faster than you gain adena proportionally. That means you will out level your own economy. eg: Imagine yourself hunting mobs lvl 50 with a top D weapon. Or a C weapon but losing money because each kill cost you money, everytime you advance mobs get harder meaning they need more hits but they don't drop more adena so you keep losing money. This is