One of the quickest wins for site performance is optimizing your images and serving your media (like videos and audio) from optimized services. This requires little to no technical knowledge and can have a BIG impact on your performance.
Additional Resources
How to Optimize Images for Web and Performance
Everything You Need to Know About WordPress Image Sizes
15 Best Image File Types (Pros vs Cons + Use Cases for Each Format)
How to Use WebP Images on WordPress (Shrink Image File Sizes up to 35%)
Lossy vs Lossless Compression: A Beginner’s Guide to Both Formats
Why and How to Use Lossy Compression on Your WordPress Images
What Is an SVG File (And How do You Upload SVGs to WordPress)?
SVG vs PNG: What Are the Differences and When to Use Them
JPG vs JPEG: Understanding the Most Common Image File Format