If you have to get one initially, go for a CRM but make sure that you can immediately set up a marketing automation system once your situation calls for it. A good CRM foundation is HubSpot CRM; not only because it is 100% free, but it is highly scalable to match your growing needs. Getting started with it is easy when you sign up for a HubSpot CRM free app here.
Marketing automation platforms allow companies to deliver promotions on, say, flash sales, to small segments of the customer universe based on targeted campaign objectives, or revenue goals for a particular territory or population. AI and analytics tools either can or soon will be able to create predictive models that can drive even more revenue with fewer customers contacted per campaign, depending on the tool and to which CRM platform it connects.