How do you say take care in portuguese?

Tem cuidado contigo or Cuida-te
1. " Tenha cuidado! " / " Tome cuidado! " / " Cuide-se!" [popular form: "Se cuide!"]

or

2. " Tem cuidado! " / " Toma cuidado! " / " Cuida-te! " [popular form: " Te cuida! "]

1 - for verb in the 3rd person, singular (subject being "Você" [*] or [] "O senhor", "A senhora"); [*] it is just a bit lighter, not formal properly; [] it is general for older people (man / woman > masculine / feminine);

2 - for verb in the 2nd person, singular (subject being "Tu", that is more intimate, but used for any informal relationship);

In plural, Words (subject pronoun and verb) endings are just a bit modified; you can learn them in next class, lol.