Remarketing is a great way to target your audience and it often has a much higher conversion rate than marketing to the masses. It is essentially targeting people that have previously interacted with your business. For example, if they have visited your website, they may then see a Google Ad on another site for your products or if they have liked a post on Facebook, their ad may come on to your news feed. Targeting customers in this way, may shrink the number of people you reach but you are more likely to reach people who are actually going to be interested in what you have to offer. Some people will opt out of targeted advertising so you may want to do a generic campaign too to ensure that you reach a wider audience.
With any sort of marketing it is vital that you keep an eye on how much you spend and what return you get on your investment. This will then allow you to make a decision as to if you want to continue with it or not. You may be able to see data from the software you use to do your remarketing or you may be able to obtain it from statistics packages such as Google Analytics.