The goals of your campaign will determine the success you achieve. Sales, conversions and ROI are the most important things to note. To create awareness, reach, impressions and engagement are more valuable. It is easier to monitor your performance by using tools like Google Analytics. Which measure do you trust most ?
Success is measured through metrics along with campaign goals. Common indicators that you need to watch are website traffic, click-through rates, conversion rates, engagement on social media, lead generation, and return on investment. Tracking these over time shows which strategies perform and which need adjustment.