Board Thread:General Discussion/@comment-24703651-20140318191358/@comment-9577979-20140318231934

Free: You can get 15 more slots after clearing Celestial Realm 1 ( Area 10-6 )

Paid:

+10 for 300 Jewels (One time use)

+20 for 800 Jewel (One time use)

+5 for 150 Jewel ( 4 times use) so in other words +20 for 600 Jewel

+20 as collection ( 400 for first 10 slots. I don't know how much the remaining 10 cost though )