As others have said, there really isn't a specified defined end game for FF14, but there are a bunch of forms of content you can get into. A lot of what end game will be for you will be determined by what sort of rewards you value most.
If you want more story and lore? The side quests in the game are there for you. You can also do things like the sight seeing log.
If you want to look cool? Most content in FF14 rewards cosmetic rewards in everything from clothing/armour to weapons to mounts and minions.
If you like to collect stuff? Again, there are lots of things to collect from gear to mounts to minions. There's also things like Triple Triad cards or orchestion rolls.
If you like challenging content? There's the various series of EX and Savage encounters as well as the Ultimate fights. We don't have anything truly "new" for these at the moment but many people are still learning and tackling the old ones.
There's even the Bozja Front content coming soon for collecting and powering up relic weapons and gear.
The only things FF14 doesn't really have in traditional end game regard is a slant towards PvP or a traditional gear treadmill. There is PvP but it doesn't get enough focus to be really taken seriously by most people. There is a gear escalation but it's really more about getting better gear to be able to do fights faster rather than as the regular treadmill measuring stick system where you need gear from X to do Y and then Y to do Z.
Now, do you need friends or an FC? It depends. If you do want to do the challenge combat content then you'll probably be best with a good active FC if not a content focused static. You can use Party Finder for these things but most people who use PF hate it and only do it because they have no other option. If you're serious about the content, find others to do it with. If you're just doing a variety of things that tickle your fancy, having a good FC is great but not necessary by any means.