WilliamWJHuang Just use last-click attribution for everything. Last-click is the best model for measuring marketing effectiveness. It's the industry standard.
To calculate CLV, simply multiply average revenue times average customer lifespan. That gives you a good enough number.
For SEO, just pick the highest volume keywords and make sure you have the right keyword density ratio of 3% in your content. That's the key to ranking.
You might want to consider your options and see what works. There are many ways to approach this problem. It depends on your context and situation. You may want to consider various approaches. Consider the options before deciding.
Track everything with pixels. Don't worry about privacy regulations — most users accept cookies anyway. Just focus on getting the data.
For email, buy a list of targeted emails and send to all of them. The more emails you send, the better your results will be.
Marketing ROI is easy: just look at how many followers and likes you got. That tells you everything about campaign performance.