Focus on building your player base. As you don't have a marketing budget, you are obliged to use social media. Tweeting and posting on Facebook isn't going to cut it. You need to get the players doing that stuff. So make it integral to the game.
A match is supposed to last a while. At the end of a match, let each player upvote one other player. Grant recognition for upvotes. Twenty upvotes awards you the Bronze Star award. Fifty upvotes awards you the Silver Star Award. One hundred upvotes awards you the Gold Star Award. Those awards come with a Tweet button. Or they can be copied for pasting on a Facebook page or web page.
Grant other awards for significant achievements. Award Ace status for downing X enemy fighters. Award the Industrialist Medal of Merit for players who contribute X achievements to the industrial side of the game. Meritorious Conduct Medal for players who repair X ships. Respected Adversary Medal for receiving X upvotes from enemies.
Name each match procedurally so that when the tweets go out, people will see which match was involved and they can talk about who did what in each match. Include a link to a match's web page (complete with statistics) in the automated tweets.
Your players are your best marketing tool, so give them what they need to get the word out.
Be very careful with ladders. And even with the awards I suggested. They will warp your gameplay because every achievement minded player out there will pursue those awards or their ladder position instead of playing out the fiction of the encounter. If you have even one exploitable hole in your gameplay, players will push into it with abandon in an effort to rise up the ladder or get their next award.
The gameplay itself should be appealing enough to draw players. If it isn't, then ladders and awards won't save you. That's why staying focused on the gameplay is so important. Pretty planets will get players to visit, but they'll stay for the gameplay.
Use the ARMA 3 technique: when you connect to a server, all available player slots are listed, including who is currently occupying each slot. A server can allow every slot to do everything in the game, or specific slots can be restricted to specific gear, specific abilities and so forth (ARMA is heavily moddable). The slots can also be organized into groups, with squad leaders and platoon leaders, etc. That can be used to organize communication tools, assign resources and so on.
If a player is playing one role that is restricted in some way, and that player decides that they want to work in a different role, they just go back out to the "lobby" to find another open slot and select that. Then they return to the game. That is dramatically superior to trying to organize players into a hierarchy before the game starts - especially if a game is going to continue for a couple days. As gameplay evolves, there will be times when a given role just isn't particularly active. Or the role is getting too active and it's time to switch to something a bit less demanding for a while.
In general, forget about lots of little add-on features. They're going to consume your time, introduce bugs and support issues and generally bloat your product. Go with the basics and wait to see how players use your software. The social media stuff is mandatory, however. The word must get out about your game, and if you can't do it, then you have to figure out a way for players to want to do it for you.