Trying to study the Queen's Gambit

I'm a novice player (rating around 1200) and I play with the e4-Bc4-Nf3 opening, something like Ruy Lopez. I'm trying to begin to play with the Queen's gambit opening, but I can't find any study material. I watched some videos but there are many variations that I don't know. I'm not a premium member and unfortunately I can't buy any books. Is there a good way for me to learn ALL variations of the queen's gambit? Where?
Thank you! 

Two things:

First off, the Ruy Lopez is NOT e4-Bc4-Nf3, the Bishop goes to b5.  This just confirms that you are not ready to be studying any specific openings.  You should be studying endgames and tactics, and then positional play after that.  Forget about openings other than opening concepts until you are 1600.  What good is opening theory going to do you when all you are facing are other low-rated players that don't know what to do beyond maybe the 5th move?

Focus on Endgames.  If you are going to try to claim you know your endgames, do you know the answers to each of these questions?  If you don't know the answer to even a single one of these, as they are all extremely basic, then you aren't ready for openings:

1) White King e6, White pawn e5, Black King on e8.  Is this a win for White no matter what, a draw no matter what, a win for White only if White is to move, or a win for White only if Black is to move?

2) White King e5, White pawn e4, Black King on e7.  Is this a win for White no matter what, a draw no matter what, a win for White only if White is to move, or a win for White only if Black is to move?

3) Demonstrate Lucena's Position.  Is this a winning or drawing mechanism?

4) Demonstrate Philidor's Position.  Is this a winning or drawing mechanism?

5) What is the Short Side Defense?

6) How do you mate with Bishop and Knight versus lone King.  Show a forcing line with WB on a8, WN on a7, WK on a6, BK on c7, White to move.

Mating with a Bishop and Knight versus lone King is extremely basic???

Yes, it is - Knight moves like an M, and the Bishop has one magical move you must know, otherwise, its role is very easy.

Just play whatever you feel. Over time, you'll figure out what works and what doesn't.

Rook endings are very difficult and yet the most common . I have played tournament chess for more than 40 years now and have only had B+N  v K  one time and have never had B+B  v K which seems also extremely rare . 

In 17 to 18 years of tournament chess, I've had B+B vs K once via intentionally because my opponent wouldn't resign, so I promoted two pawns to Bishop and mated her that may.

B+N vs Lone King happened twice, both legitimately.  Once in 1997, and again in 2009, having been on each side of it once.  Both times Black had the pieces.

Lucena's position?  Maybe 3 times.

Philidor's position?  At least 30 to 40 times.

Short Side defense?  At least twice that I can think of.

King and Pawn versus King?  A frequent occurence.

And by the way, you comment that Rook endings are very difficult.  Many are, but I could tell you the result of almost any Rook and Single Pawn versus Rook scenarios.  Very different than say, R and 7 pawns versus Rook and 6 pawns.

I believe something like 50% of all endings are rook endings and even GMs misplay them sometimes so studying them would likely pay more dividends than studying any other endings . IM Boris Kogan once told me that if I would study rook endings seriously for 1 year it would increase my rating at least 100 points . 

If you want to study it as white then you are probably better off playing e4 for a bit until your ratings increase.

As far as studying it as black goes. Well, I sat down with a couple of QGD books 6 months ago. I had a quick look at the QGA, Lasker and Orthodox variations before deciding that I would choose the Tartakower variation Thus, I learned this upto about move 13, which reaches a position I am happy playing from. Anyway, I have played a number of games on chess.com since then and normally find that people leave the book way before move 13. In fact, people often do not play Bg5 (or Bf4 for that matter). The point being that I play people 150-200 points higher than you and they still do not follow the book that closely. The amount of knowledge/understanding you actually need on the QGD could easily be picked up using a couple of websites. The one thing I would recommend you learn is the minority attack if you do not already know about it.