Welcome to Steemit and good to have another gamer around!
Main points would be to just post quality content with both length and screenshots (generally 500 words if possible or multiple paragraphs at least), or if you go to post a video, it can have less length wordwise (few paragraphs) but be of quality along with a quality video. Enjoy what you do and keep on posting.

Also make the effort to find quality posts to both upvote on and leave a nice message. I did that for the first 5 weeks, few hours a day when free and people always appreciate you taking the time to make an effort with checking out their post and leaving the message. That interaction and building friendships etc on Steemit will be a big help.

You will learn quickly and get better with using the site and other sites connected to it. So feel free to ask questions and anything to help you out and we look forward to seeing your gaming and cosplay posts when you do post! :)