There is no better way to master keys efficiently than practicing scales. In fact, you should first just give yourself time to practice only the major scales.
All 12 major scales should be practiced to a point where you can play them with both hands together for at least four octaves. You should play with an evenness of tone and the fingering should be absolutely correct.
If you focus on this, you will see the rewards very shortly, and the rewards are immense.
This might sound like boring and generic advice, but it is common advice for a very good reason.
Here's my story.
Over the summer when I was in 9th grade I went to a practice room for two weeks straight. For 2 weeks all I did was practice major scales on the piano.
I made sure I practiced them with the metronome and used the correct fingering.
I share this story with you because those two weeks changed my entire understanding of music. I learned the language of 12-tone western music by simply practicing major scales.
After those two weeks, I noticed that I became a better sight-reader. I no longer saw isolated notes on the page, but rather patterns that belonged to certain scales. I also was able to play with at various tempos, and I could even improvise over chord progressions. I was really happy when I saw how fast and gracefully my fingers could move on the piano. I'm a clumsy person, but my fingers are no longer clumsy because of these two weeks when I did nothing but practice scales.
I would recommend practicing major scales clockwise in the circle of 5ths, and then counter-clockwise in the circle of 4ths.
By doing this you get to know all of the keys, how they are related to one another, and how chords and intervals are just a part of the scales. You will notice that all of this knowledge falls into place by simply practicing the scales.
Within every major scales lies 7 modes i.e. Ionian, Dorian, Phrygian, Lydian, Mixolydian, Aeolian (natural minor), and Locrian (In fact, every time you play a major scale, you are really playing 7 different scales).
When you practice major scales you become deeply aware of these modes, and you will be able to apply them to your understanding of music theory. If you choose to compose or improvise, knowledge of these modes proves to be extremely valuable.
Spend time with the major scales - good quality time. Practice scales every day for at least an hour. I promise that so much knowledge falls into place after doing so :) By doing this, you will be teaching yourself to be able to speak the language of music.