Yeah, there’s no real substitute for making great items. Great items are more likely to sell and more likely to get you a featured file… and lots of items are more likely to get you featured author. THe better the item, the more likely you are to get into top sellers and top items, the more likely you are to come further up the results if people search by sales or trending.
There are things you can do for more exposure, but they’re not going to help that much if the quality isn’t already there. Twitter to announce new releases, set up a facebook page or group for new tracks, maybe have your own website, get people to sign up to an email newsletter, stick your stuff on soundcloud, Youtube etc. Maybe whip up a simple track or get one of your existing tracks that isn’t exactly a best seller and give it away for free when people sign up for your newsletter (after removing the track from Envato) etc.
You could try Googel ads, twitter ads, Facebook ads, small ads on music sites etc. People more knowledgeable than me will tell you which ones work and which don’t. None of them are guaaranteed… you might spend $100 in a month and get $75 in sales revenue.
Quality, quality, quality though… the 2002 classic ‘The Adventures of Pluto Nash’ spent $20m on marketing (on top of the $100m it cost to make) and it got a $7m return.