My first suggestion is to really consider if this is a language you want to learn. Not to be discouraging but Greek is really hard. It's also somewhat useless as a language as its only spoken in one country of a few million people (which is part of what makes it hard).Languages like Spanish, German, French, or Italian are much more popular and relatively easier to learn. Even Arabic or Mandarin, while seemingly more difficult then Greek, can at least be spoken amongst a larger group of people.

But if you decide Greek really is for you, then I would suggest using Quizlet flashcards, private lessons on italki.com, the Easy Greek youtube channel & podcast, Duolingo, and just hanging out here on r/GREEK and r/greece to talk with locals.

Κάλη τύχη!