It is important to understand that advertising can be very expensive, what business or startup is before. Advertising is important as it stimulates public curiosity and attracts new customers. Good start can be Google AdWords, however, try to understand as much as possible so that you can get a certain amount of return.
The biggest advantage of startup community development is the fact that they often save money. The best way to start is to outsource the agency where they will take your budget with the budget you want to set up. For example, large corporations took care of advertising. Of course you will not be able to adjust such overhead.