marketing ideas or advice needed

So im very close to finishing my unity project that I spent way too much time on and this will be the first one i would like to market on places like steam or other similar types places to sell and promote my first game. Its a simple game with 2d block based movement. The advantage that makes it fun is that it is multiplayer and can do 50+ players. So being a little guy like myself i obviously cant promise hundreds of people on a server selling the first however many copies. it does have a simple AI script to control missing players but i fear that wont keep them entertained for long. haha.

I am looking for ideas to jumpstart my campain.

free copies for a limited time? game limitations? sell maps to host? adds?

any advise?