Buy used and refurbished business laptops. They are designed to be more durable and repairable than consumer models, and are typically discarded in good condition when companies upgrade en masse. Thinkpads are a good option. Don't buy into the propaganda that says you need a new computer: Moore's law is dead and almost all personal computing tasks can be done using a CPU from 2008. Learn to replace hard drives: it will lengthen the lifetime of your own computers, and you can buy units without hard drives much cheaper.
Use free and open-source software whenever possible. It doesn't matter whether you personally want to make changes to the code: If the users as a group don't have the ability to read and change the source code of a program, its developers can and will include malicious funtionality such as spying, DRM, lock-ins, forced upgrades, and everything else that makes software horrible.
You should do most of your day-to-day computing on a free, Unix-like operating system. It doesn't really matter which one, but Linux Mint is probably the best option for newcomers. If you have to use Windows for something, you can dual-boot or use a dedicated physical or virtual machine.
Use Firefox for general web-browsing and Tor Browser for sensitive activity.
Block unwanted content on websites with addons like Ublock origin and Privacy Badger.
Avoid web-apps and cloud services where local programs and data will do. If you have to use online (dis)services, avoid giving them your personal information unnecessarily. Use fake names and throw-away or forwarding email addresses.
Use a feed-reader to follow sites and creators you like through RSS and atom feeds.
I recommend Feedbro.
Many popular websites offer RSS feeds, although they usually don't make them easy to find.
For instance If you append
.rss to almost any reddit link, it will be readable by a feed-reader.
For instance if you enter the url
in a feed-reader, you'll be able to subscribe the subreddit without a reddit account.
Likewise, you can get an atom feed for a youtube channel by appending the channel id after
The channel id is the end of the url for a youtube channel.
E.g. if you're on the channel page at
then the channel id is
and the atom feed will be at
Many sites that don't support RSS can have feeds generated through
an rss-bridge instance
Don't visit corporate content-silo's like Youtube, Twitter, Instagram, etc. directly. Instead use programs and websites that scrape content from those sites and present it to you in their own interface. For example, nitter.net will let you view tweets without visiting twitter.com. Piped and various Invidious instances will do the same for youtube videos. These options are better for privacy, and also tend to offer a superior experience. You can use the Privacy Redirect addon to automatically redirect to those sites when you follow a link to a content silo.