In a startup you should be review your strategic opportunities at least quarterly. In big companies, you'll start this planning in early Q3. You'll then go thru several months of vetting and enter into what I call the "strategic planning thunderdome." Fans of the Mad Max films will remember this reference, "two men enter, one man leave." Please do not do this in a startup. It is not meant to be a political death match. There is no internal posturing required. This is a startup and you are trying to build a business. Do not expect to have all of your operating variables known. But, you should have a planning process that is lightweight yet thoughtful.
This is a useful template when you are sitting down with your team. Download strategic_planning_diagnostic.pdf You are typically balancing how much you are optimizing for market share, revenue, or EBITDA. Most likely as a startup with fast mover advantage you'll be optimizing for market share. Think about customer, supplier, and your overall mix (share, revenue, or EBITDA) when assessing where you want to focus. For example. at WidgetBucks, we're optimize for customer value over supplier. In other words, we value share and product innovation to publishers and suppliers over working with direct brands. We'll get there eventually but its not the right timing yet (its right when we're big enough where they will want to work with us). Take your strategic assumptions thru your prioritization criteria and you'll quickly and easily get to the top 3-5 initiatives for your company.
Remember to not stare at your proverbial navel too long. Do this once a quarter. Get your team involved, agree, and get moving. Speed is your advantage but don't try to do too many things at the same time.