Hi how are you VeeOnline.
When is comes to online growth for a website. This comes in many ways. The first question you need to ask yourself is what the client's goals and the sales funnel for the client. In most cases, most clients care about the money that comes in their bank account. They don't care much about the processes.
This takes you as the digital marketer to analyze your client's business and come up with a plan. What i have seen that worked well for most of my clients is paid ads. If you can focus on paid traffic you will bring growth to your clients much faster. If they have optin on their website, make sure you send paid traffic to the page. If the client wants to grow thier following, you again use paid ads.
Speaking of paid ads there is facebook ads, twitter ads, google ads and so much more.
In short go for paid ads
Let me know if you have any other questions.