Hello Nicolás,
It's great to hear that you wish to start a new translation of Moodle! You can certainly develop the translation incrementally; actually if you look at the Language packs for Moodle 3.3 you'll see that very many translations are a work-in-progress.
Please see the doc Starting a new language pack for details of how to volunteer to start a new translation.
Regarding which words to translate first, we have a guide Translation priority to help new language packs to reach a usable state as quickly as possible.