This is doamatto.
It’s always good to keep your data secure. If you can’t or don’t know how to self-host services, or you’re the average person and you don’t mind other people storing your data as long as its handled well, this is the checklist for you.
Keep all your passwords different, use two-factor authentication, and use a password manager. I personally recommend Bitwarden; it’s free, open-source, and is cheap if you want to have a family connect to one vault or have premium features like TOTP storage and more. Don’t store passwords, credit card info, or addressses in your browser’s “keychain”, nor in a service like Apple Keychain (through iCloud, that is) or Google’s password management solution (whatever it’s called).
When sending messages on iOS to iOS, you’ve got iMessage, which is generally solid. However, SMS is poor and, for that reason, I, as well Snowden, recommend Signal. It’s secure, encrypted, and simply works. It also supports SMS, just in case you find someone without both iMessage or Signal. I also recommend Keybase.
For DNS, you should use Quad9 (188.8.131.52, 184.108.40.206). The Foundation for Applied Privacy’s DNS service got a 10/10 in my evalution on PrivacySpy, so it’s a good consideration as well (Quad9 got a 9.8/10 for very, very minor things).
For email, I use Protonmail and Tutanota. Both are solid services I can easily recommend. If you don’t mind not being able to use your doamin, though, consider Posteo. It’s realtively cheap, private, and prides itself on being a green service (they use only renewable energies)
If you don’t mind the inability to sync with your dialer, contacts, calendar, and tasks apps, you can use Protonmail or Tutanota as they both have contacts and calendar support (ProtonCalendar isn’t quite yet out as of writing, but is nearing release. If you do like the ability to sync, you can use EteSync. It has end-to-end encryption (E2EE), and is also stored with zero-knowledge encryption. EteSync has their own DAV bridges, as well as their mobile apps syncing with the apps on your phone.