Start with the funnel
Before choosing a social or advertising course, understand the basic path from attention to landing page, follow-up and conversion. That gives channel tactics somewhere to fit.
Use a broad overview first
Digital Marketing Overview is useful when the relationship between content, email, landing pages and other channels is still unclear.
Add social-media context
Basics of Social Media Marketing makes more sense after the funnel is clear. Platform examples change, so keep the principles and re-check current platform documentation.
Study advertising when measurement matters
Digital Advertising and Marketing 101 is more relevant when you need vocabulary around targeting, ad formats and reporting. Do not confuse learning ad terminology with being ready to spend money on campaigns.
Build one measurable experiment
Choose one audience, one offer, one landing page and one metric. A small measured experiment teaches more than collecting disconnected tactics.
Decision rule
Learn the system first, then the channel. If you cannot name the metric a tactic should improve, you are probably not ready to add another tactic.