What exactly can be done in a party

So I got into the game about a week ago and a buddy of mine just got it last night. So this morning I told him we'd party up when I got home and do some stuff.

It's occurring to me now that I don't know what that stuff would be. Much of the main story and class quests seem to be solo instances which I assume I can't help with. He hasn't unlocked any dungeons yet so I can't help him there. Is there anything we can do besides grind fates? If he takes a guildleve for instance, won't I be locked out of it?

You can both to guildhests or leves together in a party. It's hard when he hasn't unlocked dungeons yet, but you can easily communicate with each other in party chat without going the long way of /tell. Apart from that, do you both like to RP? Can be great in a party!

other than what you already know, the choices are very limited due to him being new and a lot of stuff not set to the party experience like ff11 was. Though my friends like to join together an journey the story together. They split for the solo stuff and re join to journey again lol I join them in their Duty Finder stuff.

Cool. I'll basically just run around with him and help where I can, hit up some guildleves, fates, etc. It won't take long until he unlocks the first few dungeons anyway.

Leves can be pretty effective with multiple people. Problem is that if he just got the game he has no level allowances until level 10 and those will go quickly. You can easily guide him around and what not though, even though I personally think the game does a pretty decent job of that by itself.

I may be wrong but believe that if you have a party for boss fates for instance you can also build up your meter and use limit break.
I swear i have seen it before, again just speculation as i normally always solo or go with a Fc member to fates.
Leves are shared with people if you are group.
The solo instances in this game are mainly the class quests which i think makes sense, some however can be joined by others.

I have to start leveling my alt class so I'll switch to that so we're closer to the same level then just do whatever we can together. If he gets pulled into a solo instance I can just craft for a bit while I wait I guess.