There are tens of thousands of populated worlds in Star Wars and even more factions. Some span the galaxy entire and some are limited to a single village, but their size doesn't make them any less or more important when crafting a good story. While there are many, many in-universe factions to participate in, sometimes the best faction is the one you make yourself.
The following are the rules for making and running an independent player faction:
Rule 1, Everything must be done in RP.
Creating a faction is as simple as talking in a chatroom with a few friends and deciding that you're now a faction together. However, in order for your faction to have assets and material, in-character threads must be done to acquire these things. Rather than list every item that can or cannot be gained in a single thread, I will link you to rules 2 and 3 here.
Rule 2, Earn it.
Everything you desire must be worked for. Starting an RP for the sole purpose of creating a capital vessel, stepping onto it, and declaring it yours will do nothing more than waste your time and my own. Such a thread will be voided. If you want to find/buy/steal a starship, run a thread getting together a crew and setting up a plan for taking/buying it. Then, run another thread performing the actual job. The more effort you put in, the more you'll get out.
A simple metric to follow is this- think of the process in the real world by which people and entities gain assets, and stick close to that. No one is going to give you an expensive car in the real world for free, you must earn it. Sometimes earning it means stealing it, getting the vin number removed and re-registering the car under a different name. But as far as this rule is concerned, you've earned it.
Rule 3, Non-Player Factions
Non-Player Factions, such as existing factions or invented ones, can only be taken over through DM-run quests. While possible to become the leader of the Exchange, perform a hostile takeover at Czerka, or even be elected Supreme Chancellor, these things cannot be done independently of the DM. Please contact myself either here on RPF through private messages or at my discord #blacknoise
Rule 4, Write with good purpose.
The whole point of my allowing independent factions is to allow for more free-form RP and interesting stories. A mercenary rising from the gutter to lead thousands in unified strength makes for an amazing story. However, using the idea of a faction solely for the desire of gaining power over others in the RP is not only in violation of our Golden Rule but isn't a good story. If you want to make a faction or take over a faction, go for it! But write with good purpose, because when you rule an entire faction you must inherently work to create good stories for others as well as yourself.