Hello Valiken!

All the current raid dungeons in game require at least 2 (level 25 one) or 4 (level 45 ones) players to enter. You could probably solo the level 25 one as level 50, but you would have to get someone to let you in. The higher level dungeons aren't soloable.

There is an open world dungeon called Sphoshae in La Noscea very close to Limsa Lominsa. There are treasure chests and boss NMs and you might like it. It's planned for a level 15ish group, so I don't know how it feels like at level 30 though. I recommend you give it a try and see how it goes.