Best chess openings to study for beginners?

What are the top openings to know going into my second week of chess? I feel like a lot of the time I listen to people online about what openings to play, but half the time people always play either the one defense that was never covered in the course, or super rare openings. To add, how do you defend against an opening you don't know?

As Black: 
vs. 1. e4 play e5 
vs. 1. d4 play the Queens Gambit Declined. 
As white I'd recommend playing the Italian, which is 1. e4 e5 2. Nf3 Nc6 3. Bc4
Start with the most classical openings... focus on basic concepts like rapid development, controlling the center, and tactics.

Rat-man has a very good point, I'd simplify it further, consider playing the Center Game, Scotch or Bishop's Opening instead of the Italian, they are even more straight forward.

That's why when studying the openings the goal is to learn to understand the reasons behind the book moves as well as to understand the typical plans and strategies of the chosen opening variation rather than just memorizing moves. Memorizing moves without understanding is often pretty useless.

When just starting to learn chess I would not recommend to spend too much time if any trying to learn concrete opening variations. One should largely manage by just learning the general opening principles (critical importance of development, importance of centre, using all your pieces, importance of king safety and castling etc.). The games between beginners will almost invariably be decided by rather large tactical mistakes later on so if you want to do some other training besides playing I'd recommend concentrating on basic tactics.