1) your mother tongue

2) and 3) whatever rocks your boat.

1 English

I don't even have to explain

2 French

It's the official language in 28 countries and it's spoken fluently by 220 million people and other 200 million people have a basic knowlegde of it. It's the second most popular foreign language, after English

3 Spanish

Unlike English and French whose most speakers are not native speakers, Spanish is the mother tongue of more than 400 million people worlwide. With Spanish you can travel from Argentina to Mexico and even to the US.

I think most important language is english but third and second one  depend on  your future plans. for example, i am electrical and electronics engineer so mine is german and japanese. of course, these are my opinion.