Your marketing plan identifies your key audience, the best marketing methods you should use to reach those particular demographics, and the amount you intend to spend on those methods.
You need to define your customer base. This can change from year to year, and only by targetting key demographics will you know which marketing methods to use. Some demographics can be reached through radio, while others spend more time online.
List your expected expenditure, and your expected return on investment. You should also investigate methods through which you can identify how much your marketing spend is actually netting you.
As a start-up, you should also add marketing strategies into the plan that won’t cost you anything, such as your social media push and your SEO plans.