Building my Opening Repertoire

Hello! I am an intermediate level chess player (1500 Elo) and I am starting to get serious about chess. At this point, I am trying now to focus on building a solid repertoire for my openings. As such, I have a few questions.

1: How do I do this in the first place? 2: How many openings should I memorize? 3: Are some better to learn than others? 4: How many should I learn for white and black? How do I avoid becoming bored of playing the same white opening over and over again.

Thank you for your help on this matter!

I wouldn't think about it in those terms, ie. setting goals of learning x number of openings to x depth by x point in time or by x rating.

You gradually layer opening knowledge as you gain experience. Instead, I found the most effective way to train openings was just to learn one opening until you have relative confidence with the types of positions that opening leads to. THEN, start with the next one, in order of probability of facing. So for me, it looked something like this:

Choosing one main opening to play as white, eg. Ruy Lopez, Italian, Scotch, whatever it is you want to play vs 1.e5 (If you're a 1.e4 player). Then, learn the main variations of that opening. I'd also recommend choosing reputable side-lines in your opening choice, because whenever you play the main-lines, chances are you'll always run into people who see it all the time and know it better than you do. 
Once you're comfortable with the majority of actual positions you tend to get into from this opening, rinse and repeat this process with the other most common openings you face. 
If you're an e4 player, the list of openings by probability will likely be:
1. e5
2. Sicillian (although once you reach around 1800, the Sicillian will likely switch to being the most frequent opening you run into vs e4).
3. French
4. Caro
5. Pirc/Scandi/Modern
6. Follow opening principles against everything else until youre confident with the above.

I'd always recommend the most aggresive or tactical variations possible against any given opening.
I'd then build my opening repertoire using the database vs players as well as searching youtube for that opening name to learn more about the practical/human ideas behind those moves. I then plug them into a pgn and start building a file. Then, drill them in blitz! Then, analyse your game results by opening choice (using explorer or openingtree.com) to measure improvement.

Pick one opening for white and one as black that you like to play.

Then consider what you do when your opponent plays something less common.

For example, when my opponent plays 1.e4 I play the Caro-Kann Defense.

When my opponent plays 1.d4, choose either 1...d5 opening of 1....Nf6 opening and learn that.

When I am white I open with 1.e4. This is several openings.

If opponent plays 1...e5 decide on an open game opening. Vienna, Ruy Lopez, Italian, Scotch are all good choices. Pick one and stick with it.

If opponent plays 1...c5 Sicilian Defense, have a plan for how to play against that. This could be open game, closed game, or one of the many anti-sicilians.

If opponent plays 1...d4 Scandinavian Defense, have a plan for how to play against that.

If opponent plays 1...e4 French, have a plan for how to play against that.

If opponent plays 1...d6 Pirc, have a plan for how to play against that.

If opponent plays 1...Nf6 Alekhine's Defence, have a plan for how to play against that.

Certain openings come up much more often than others depending on what rating level you are at. 1...e5 is very common at all levels so more time should go into how to play against that than against 1...d6 for example.

Start off with about 5 moves and gradually build up over time. After your game look at the first bad opening move you played and see what you should have played instead and try to remember that.

Then over several years and thousands of game you gradually build up an encyclopedic knowledge of openings.

On not becoming bored with the same white opening, your opponents won't let you play the same opening every time, you will need to learn the above options for 1.e4 or others if you play 1.d4 or something else. So you will be playing different openings whether you want to or not.

But don't play 1.e4 one game and then 1.d4 the next and 1.f4 the game after for the sake of mixing it up. Play at least the same first move every time.

Daily games are a good way to learn openings because you can use the opening explorer which is based on master games.

Another way is to play blitz games and analyze your opening after each game.

Chess Openings Resources for Beginners and Beyond...

https://www.chess.com/blog/RussBell/openings-resources-for-beginners-and-beyond

https://www.chess.com/blog/RussBell

@1

"building a solid repertoire for my openings" ++ Not necessary, that will not help you.

"1: How do I do this in the first place?" ++ Just play and analyse your lost games.

"2: How many openings should I memorize?" ++ None at all.

"3: Are some better to learn than others?" ++ All main openings are sound.

"4: How many should I learn for white and black?"
++ Learn: none: play: 1 for black against 1 e4, 1 for black against 1 d4, 1 for white.

"How do I avoid becoming bored of playing the same white opening over and over again."
++ Professionals play the same openings in hundreds of games without getting bored.
The more you play an opening, the more you accumulate experience and the better you play it.

You have to play an opening long enough to understand established lines and the positions and tactical opportunities they lead to. Once you do this for several openings, you find both structural and tactical strengths and weaknesses. You learn how to exploit the former and avoid the latter, and in that there's a different type of system/aesthetic for different opening systems.

And since most known openings are perfectly sound, it's a matter of personal style which ones you hold in your arsenal. So yeah, experiment, go into depth, discard openings you don't like, and you are likely to end up playing just a few of them in the end - because they get you into a chess system that best matches your individual way of thinking. O-pe-nings: Gotta try'em all!