I use firefox, so I'm not positive if all of these are available for chromium based browsers.

Each extension varies in how big it is, so there isn't an easy rule for how many extensions to use. Also, if you're trying to increase privacy, many extensions can make your browser fingerprint more easily identifiable.

• uBlock Origin - I have it set to block everything by default like NoScript, whitelisting sites as I use them. I used to use uMatrix for this before it was discontinued, but this works well enough.

• Tridactyl - Advanced vim-like keybindings. It has more features than something like Vimium, but I've had it occasionally break sites so I had to change the noiframe settings listed on the troubleshooting page.

• Midnight Lizard - I've been using this lately instead of Dark Reader. It has much more customization, but I've occasionally had it mess up on some sites.

• CanvasBlocker - Sends out fake info to make your browser fingerprint different each time. This doesn't fully prevent fingerprinting with how I have my add-ons set up, but it at least makes the job harder for trackers and gives them less real data.

• Local CDN - local copies of common libraries, so you don't access a bunch of 3rd party sites to download javascript. This sends your data to fewer sites, but if you're trying to stay anonymous it makes your fingerprint more unique.

• AutoTabDiscard - This unloads inactive tabs, which comes in handy if you have a ton of tabs open. You can disable it for any sites you always want to keep active. You can also tweak how many tabs to keep open and how long before it tries to discard them.

• Leechblock NG - Set time limits for how long you want to spend on each site. If you use it right it can help break addictions to certain websites.

• Stylus - I use it for a couple of sites that just have really terrible styles or don't work well with dark mode.

• AutoFill Forms - Handy for if you have any repetitive forms you need to fill out.

• DownThemAll - I don't use it often, but really useful when there's a bunch of links to download.

• ViolentMonkey - Per site custom javascript. I don't use this much, but occasionally comes in handy to make a website do what you want.

• Tab Reloader - for sites that you want to keep refreshed.

I've got a bunch for integration with various websites and software:

• Plasma Integration - This integrates stuff like video playback and notifications into KDE. Also needs a package installed to connect to. There's also Gnome Shell Extension, which does a similar thing for for Gnome.
• Flatline - Install flatpaks more easily from flathub website. I usually avoid flatpaks, but it's convenient for when I do.
• Mastodon Simplified Federation - More easily interact with other mastodon sites to forward to your server.
• SponsorBlock for YouTube - I really hate ads.
• Bypass Paywall Clean - This gets around paywalls for a bunch of news sites. It's not on mozilla's add-on page, so need to get it off gitlab.
• Pinboard Pin - for my bookmarks.
• BlueLiteBlocker - I rarely go on twitter, but blocking all the top replies with blue checkmarks makes it slightly less terrible.
• RedditEnhancementSuite - I don't use reddit much lately, but when I do, this makes it more usable.
• moderator toolbox for reddit - mod tools for reddit
• TinEye - just adds a right click option for images to do reverse image search.

I'm pretty sure these are Firefox only, but I'll leave them here for anyone else who's interested.

• Simple Tab Groups - I like using this to organize my tabs into groups. There's probably better ways to not have so many tabs open but it's convenient to have a bunch of open tabs when I want them.

• Multi-Account Containers - Helpful if you have multiple accounts on the same site, or want to keep your cookies separate for different tasks.

• Firefox Translations - adds more language options to Firefox's offline translation.