My Titan is rank 5 FWC, Rank 2 New Monarchy, Warlock is Rank 1 New Monarchy, Hunter is Rank 2 New Monarchy. I like their weapons better in New Monarchy and got my FWC weapons from engrams.

I heard tell level 10 gives you a special shader.

I'm almost Rank 6 with Dead Orbit. Every rank you gain past Rank 3, that Faction sends you a Legendary gift through the Postmaster. I've received the Dead Orbit Fusion Rifle, Oblivion Gauntlets, and Rocket Launcher from ranking up in the past (hoping for their Auto Rifle since i accidentally destroyed the one I bought...), but the package could also be Legendary upgrade materials, Motes of Light, and Strange Coins. It's like the RNG, but with a smaller pool of options because any weapons and equipment are from that Faction (which is cool in itself). That, and I have a sneaking suspicion that they're going to include stuff in later updates and/or expansions that deal with the Factions and having higher and higher Rank. I have nothing concrete to go off of, just a feeling I have.

Nope you really just get more purple gear and what not

It give something at the postmaster whenever you level up, another method to get legendary gear.

Good Day! New Clan based around Future War Cult. We wear their emblem, class armor and weapons as much as possiable to show unity for the faction. You are no way bound to any weapon or armor. I just believe that the FWC holds the most appropriate philosophy in the game. I want my clan to have that style. DOW will march together in PVP or PVE. Anywhere. [quote] We Can We Wiil [/quote]

If it's anything like the cryptarch you will get items from the postmaster to collect every time you level up