What I learn from past client and former boss in the Digital Marketing
Know your KPI and test conservatively
Here an example
From Facebook Pixel, I can create a custom audience, then later re-targeted through the Facebook ad manager
7 days is a good sample if it works or not
Use Google Adword keyword planner to search for key word for SEO then bids for the keyword.
I use SEM rush and Arefs for additional research.
Test conservatively on the Google Ads and if it works make an A/B test to further optimize the ads.
Use Google Analytics to analyze the traffic coming from the website