At lvl 10 you can open up Guildhest after finishing your first Guild Leve and then another quest to talk to the Guildhest NPC. They are bite sized instanced quests that come across as a tutorial for group play. They only take like 2-10 minutes each, really quick and first time you do them give really, really nice EXP. EXP is significantly less the second time around but as long as you dont die during the quest you get still some decent EXP. Got like 5k EXP first time on the lvl 10 quest and then 900 EXP each time I did the lvl 10 ones after, it goes up obviously with the level range. The Dungeons don't open up till AFTER you complete the airship envoy mission line at lvl 15 for the main story, then you go to Satasha in Western La Noscea and open up the first dungeon. There are 3 start dungeons you do in order. Afterwards there will be quests unlock higher lvl ones and several others won't unlock till you are at a specific place in the story and then you can repeat it as often as you want from there.