About Tattoos … every Tattoo that you equip gives about minus 5 P Def … Don’t know how and why it happens but it does. Otherwise if you see a reduction in any of stats (usually P def, Atk Spd and Cast Spd), it is the result of your character not being the right grade yet. However, if you are the right grade, there should only be positive effect added to your stats.
About Drops … the only thing you should worry about getting dropped from mobs is adena (even that gets useless at higher levels though). When you will reach the point of the game, where materials are needed, create a spoiler (or two spoilers) and gather everything you need. The server has custom spoil list (can be found here) and you can gather materials this way very quickly.
Hope this helps and see you soon. 🙂
It is not that you do not understand, it is that you do not even question.