There's a lot you can do for free first, but it takes a bit of work and persistence.
*Put together a nicely composed e-mail along with press kit containing screenshots, video and link to game.
*Email it to magazines, local newspaper, gaming sites, reviewers, editors, youtubers, twitchers etc.
*Be active on social media, engage people.
*Hand out flyers with promo code outside your local supermarket if you have to.
*Attend some games conference or other related gathering to promote your game, if there's any related in your area.
But most importantly! Spend some extra time to polish up your game, to make things as good as you can. Polish the artwork, controls, gameplay, performance, press kit, game description to the best of your abilities, and look what other successful games are doing. That extra Mile will show through, and all players can differentiate between a well made game and a sub-par one, and if they like your game, they will recommend to their friends, coworkers, family, and downloads will grow naturally.