UBlock Origin obviously. out-the-box works just fine but has a bunch of extra privacy/tracking/spam filters you can enable
Decentraleyes protects you against tracking through "free" curated content delivery and works alongside UBlock (or any of the other common adblocking addons)
I Don't Care About Cookies good for EU users where GDPR made it so every site ever in the universe asks you to accept cookies and privacy terms seventeen times a day. will just auto-accept for you. never see an annoying popup again! but only use in conjunction with...
Cookie Auto Delete does what it says on the tin. will automatically flush cookies, cache, and data when you close a tab. those cookies you just auto accepted? they're gone now. whitelist any sites you wanna stay logged in on and let the rest fucking perish
Don't Track Me Google removes that annoying link conversion when you copy google results. you know when it changes from "site.com" to "encrypted.google.com/randomnonsensefor200charactersblahblahblah"? yeah. this stops that happening. fuck off, google.
Don't Accept image/webp blocks sites from using the most useless file extension known to mankind so you can save as .jpg or .gif as god intended. fuck webp. seriously. what even is that.
Bypass Paywalls Clean exactly what you think it is
HTTPS Everywhere automatically adds ecrypted security to any site that supports https (you can do this manually by adding the s yourself to any url but... who can be fuckin bothere amirite? this does it for you)
Google Search Filter allows you to remove domains from your searches forever. pinterest? gone. weheartit? nuked. also works on duckduckgo. never type "-pinterest" into a search again.
Simple Tab Groups allows you to group tabs together and shove them out of sight, which is nice if you're researching something and don't want 50 bajillion jstor tabs clogging up your normal browsing session