I am writing this topic for the reason that many players do not know how to unlock their inventory completely in-game, which is essential for good gameplay, have the inventory completely open.
1 Cube (Buy from the starting city Ishalgen or Poeta)
Row 1 (Default: 8 slots)
Row 2 (Default: 16 slots)
Row 3 (Default: 24 slots)
2 Cube (Buy in the artisan close to a broker in both faction of main city)
Row 4 (Default: 36 slots)
Row 5 (Default: 45 slots)
Row 6 (Default: 54 slots)
3 Cube (Buy in the same artisan the first line, upper abbys artisan(top island), and the last line doing a quest)
Row 7 (Default: 63 slots) -> same artisan as before
Row 8 (Default: 72 slots) -> artisan in upper abbys (top island) Jarumonerk NPC
Row 9 (Default: 81 slots) -> Quest (Asmo) Unexpected Reward or (Elyo) A Lucky Day
4 Cube (Another quest and item-shop upgrades)
Row 10 (Default: 90 slots) -> Quest (Asmo) Winning Vindachinerk’s Favor or (Elyo) The Legend of Vindachinerk
Row 11 (Item shop pack)
Row 12 (Item shop pack)