The most important thing in my life are making money, traveling abroad and to live well.
which used incorectly
should be things
also, in agreement with the other gerunds, living well would be better.
In the sentence you provided, the word "are" is used incorrectly. The correct word to use in this context is "is".
Explanation:
When referring to multiple things or ideas, we use the plural form of the verb "to be" which is "are". However, in this case, you are referring to a singular noun phrase "The most important thing in my life", which means we need to use the singular form of the verb "to be" which is "is".
Corrected sentence:
The most important thing in my life is making money, traveling abroad, and living well.