If you can't find your next story quest, check if you have Recommendations unlocked. If you are on PC, you have to click on the list looking icon in the micro menu. Not sure where it is in the PS3 menu.

Otherwise, try going back to the adventurer's guild in your city to see if there isn't a quest there waiting for you, and don't forget to do your Class Quests as your Level 15 quest gives you an extremely useful skill.

Gladiator will be very important for you if you want to level Warrior. Not only is it required for you to get level 15 Gladiator to unlock Warrior, you will also get several defensive buffs and extremely valuable tanking tools, like Flash which is a short range AOE spell that gives you enmity, and Provoke which instantly match your enmity with whoever has the highest, perfect for those emergency moments where you die, get raised, and need to get hold of the enemy again.