As for the Berserker Title, it's just a costume for Luke. Problem is, there tends to be a glitch where you can't get it on any consecutive playthrough so you need to get it on your first playthrough.

C-A

Set the game's difficulty to Hard or higher and defeat monsters around Engeve and probably Cheagle Woods too. Farm near the end of the game.

To check on how much grade you have accumulated, go to Keterburg. Head to the casino. Speak to the person where you can exchange Gald or Grade for chips. Choose Grade then the game will show you the Grade you have.

The Berserker title gets you a costume for Luke when equipped. For me, it looks awesome on him. IIRC you need to have 256 battles on Hard or higher.

Wait to get the Blue Dice (+20% grade) from an extra boss (avaible before final boss, if you don't already know about it check the Catalyst Weapon sidequest).
You should already have a Dice (+10%) from a previous boss battle, and equip them from an extra grade bonus.
I did that while finishing the cooking titles (on hard of course), and got enough grade to buy everything.
I do like the world map region near Engeve better than Cheagle Woods because of the loading time between each screen.