4 level 1 players start in Limsa

[Curisu]

As premade group of 4 you are able to go together into the dungeon, even without a healer.
It might be a bit harder and takes longer but you still should be able to clear it with 1 tank 3 dps.

Also, as small advice. Just have 1 player buy the game and sub.
Everyone else should be able to stay with the trail version until the end of the level 60 expansion.
That could save them 1-2 months of sub payment.

The one player who pays the sub is able to invite the friends into groups and to queue into dungeon together.

[BRVV]

As premade group of 4 you are able to go together into the dungeon, even without a healer.
It might be a bit harder and takes longer but you still should be able to clear it with 1 tank 3 dps.

I want to add: Arcanist has a healing spell even as a dps. So you can go in with 3 dps and a tank and the arcanist could spam his healing spell. You can also all spend some gil on potions and give them to your tank.