General

Level 70 Kaiser special Mb

I got my Kaiser to level 70 and I could get a special mastery book here are the lists:
Giga Wave 30
Dragon Barrage 30
Advanced Tempest Blades 30
Unbreaking Will 30
Expert Sword Mastery 30

What book should I get out of these? I want a book that would cost pricey at the future & could improve my stats. Thanks in advnaced.