Recommended Browser Addons

Surfing experience

DarkReader - dark mode for all websites
DontBugMe - allows you to log into a lot of pages using throwaway accounts from BugMeNot
Gesturefy - mouse gestures (Firefox only)
LocalCDN - caches remote CDN for speed and privacy
Simple Translate - quickly translate selected text with Google Translate in popup. Can be not private as it uses Google Translate
uBlock Origin - the best way to block advertisements and trackers

Performance improvement

Decentraleyes - local cache for free CDNs, also protects from CDN tracking
Total Suspender - automatically suspends inactive tabs

Security and Privacy

Cookie AutoDelete - automatically delete cookies when you close tab. Has whitelist and so on
HTTPS Everywhere - force encrypts your communication with many major websites
Privacy Badger - automatically blocks tracking pixels and buttons
Privacy Redirect - Redirects Twitter, YouTube, Instagram, & Google Maps requests to privacy friendly alternatives - Nitter, Invidious, Bibliogram, & OpenStreetMap.
PrivacySpy - simplified privacy policies and privacy policy ratings for websites
Terms of Service; Didn't Read - displays a popup when you open website with hostile Terms of Service
Trace - spoofs a lot of fingerprinting-related browser parameters, makes fingerprinting and tracking very difficult and expensive.

Please do not rely on fingerprint-resistance addons and tweaks for anonymity if it's critical for you. It's better to just use Tor Browser without Tor if you care about your digital fingerprint. It's even better to use Whonix to completely hide your fingerprint.

Firefox containers

Firefox Multi-Account Containers - panel button and menu for container management
Termporary Containers - disposable containers on the go
Amazon Container - container for Amazon
Facebook container - container for Facebook and Instagram
Git container - container for Git hosting providers (GitHub)
Google Container - container for all Google services (YouTube f. e.)
Reddit Container - container for Reddit
Twitter container - container for Twitter

Consider manually creating a container for VK as there is currently no working VK container extension.

Website improvement