It depends on the goals. If your goal is to get people from ads to your website - you are successful in having a high traffic rate. (CTR) If your goal is to have many purchases, then higher conversion rate. Your success depends on the set goal, numbers you set and then it should be clear whether you achieved them or not.

Hard to pick just one! Depends on your primary campaign goal. If it's drawing traffic to your site, then click through rate (CTR) is key. If you're more focused on sales, then conversion rate will be your north star metric. Set clear targets up front based on what success looks like for your specific campaign, then track religiously to see if you hit them or not. Iterate and optimize from there!

I wouldd say the most important metric of success for a campaign depends on its specific goals. For example: - If it’s a brand awareness campaign, metrics like reach, impressions, and engagement (likes, comments, shares) are key. - For lead generation, it’s all about conversion rates and of course the quality of leads coming in. - For retention or upsell campaigns, customer lifetime value (CLV) or repeat purchase rates is a good focus. That said, a common thread across all campaigns is (as @mehvish_shafiq already mentioned) ROI – whether in monetary terms or time invested. It’s not just about how much buzz a campaign generates but whether it moves the needle toward your broader business objectives.

I think the most important metric is ROMI - Return Of Marketing Investments. The rest is secondary.