User712890 best way to start is working on a more detailed threat model as there is no such thing as "true privacy", only privacy that fits your very individual needs. If you want to go all in, I recommend the linddun method.
After that, there are just a few general rules in my opinion:
- The less data you share, the less it can be exploited, leaked, sold etc. (e.g. use less apps and services if possible)
- Compartmentalization is a great way to not give a lot of information to the same company (e.g. use alias mail addresses, different devices/profiles, etc.)
- You need to use a good password manager and generally good security opsec (in most cases your privacy is worthless if your security is breached)
- Take it easy. If you're not on on a very high threat model, do one step at a time and don't make your life and the life of your loved ones unnecessarily hard.
As for specifics, I can only tell you my answers for my threat model, they will likely not match yours. But here are my most important apps anyway:
- Bitwarden for passwords (salted, even Bitwarden doesn't know the full passwords)
- Aegis for 2FA
- Tuta for Mails and aliasing
- Mullvad to hide my traffic from my ISP
- silent.link for anonymous eSIM (in one of 2 devices where I need one)
- Gadgetbridge for any wearables
I made a more detailed post in this thread which was already linked by kyo. Hope it helps.