If you find word-by-word translations helpful, you can always remember that it's often possible to understand these parallel to how you use qui, que, and dont already. If que and qui mean "that/which", ce que and ce qui mean "the thing that/which". If dont means "of which", ce dont means "the thing of which".
Those don't sound very natural without context, though, so you might prefer this summary:
- ce que stands for the direct object of a verb. It's usually translated "what".
- ce qui stands for the subject of a verb. It's usually translated "what".
- ce dont stands for "de" + the object of a verb. It's usually translated "what ... of".
(Wait a second for this to make sense.)
And unlike que, qui, and dont, all of the above could start a sentence when they fill the same role.
Let's try them out.
Ce qui m'aide le plus, c'est pratiquer beaucoup.
What helps me the most is practicing a lot.
→ Note that ce qui has replaced the subject of "help".
Ce que j'aime le plus, c'est jouer du piano.
What I like the most is playing piano.
→ Note that ce que has replaced the object of "like".
Ce dont je suis fier, c'est que je n'abandonne pas.
What I'm proud of is that I don't give up.
→ Note that ce dont has replaced the object of "am proud of".
Now that we've seen how they work, we can check your sentences.
J'ai reçu un e-mail du recruteur ce qui m'a informé ...
I received an email from the recruiter what informed me...
"What" doesn't sound right here, and neither does "that which" (if you're ever unsure, try both). So we should just use qui "which".
J'envisage ce que j'habiterai dehors du pays dans 10 ans.
I envision what I'll live outside of the country in 10 years.
"What" doesn't sound right here either, and neither does "that which". So we should just use que "that".
Ce dont il a honte c'est ses échecs.
What he's ashamed of is his failures.
Yes, that sounds fine. Keep ce dont here!