My fingers have a tendency to slip off the black keys on my piano keyboard. Is this because I’ve only been playing about 6 months and my technique still needs some working on or there anything I can buy that I can apply to my fingertips that will give them some ‘grip’? Thanks.
All of the things that alephzero says I would repeat. I also have some other observations.
You can go about this in two ways, and should work with a combination of both. The first is the "macro" level that alephzero describes: your hand position, your posture, the distance you sit from the piano, and so on. All of those things are important, but they won't correct your problem on their own -- there isn't any "magic hand position" the knowing of which will bestow proper finger technique. Each person is built differently, so each person's technique is a bit different. These things are general guidelines which will help you go in the right direction.
Not to be facetious, but the reason that your fingers are slipping off of the black keys is that you aren't hitting them precisely enough. They slip off when you don't strike them in the middle, and they slip off when you strike them at an angle. The only way to correct this is, well, to stop doing it. You have to be more precise in the way that you approach the striking of a key.
Easy enough to explain, but not easy to do. Trying to learn it by going through music that you want to be able to play isn't very efficient, meaning five years from now you are unlikely to be entirely happy with the results. At six months, it's time to begin looking at scales.
Scales have several innate challenges. The most basic one is that you are essentially doing the opposite thing in one hand that you are doing with the other, since your hands are mirror images of one another and you are going in the same direction with each hand. You're passing thumbs under fingers and fingers over thumbs at different times in each hand, and you have to struggle at first to keep the wheels from coming off. As you begin to solve that one, you will find that some notes are more awkward to play than others, typically involving thumbs, passing fingers over thumbs, and passing thumbs under fingers. Once you start noticing that, you can give yourself a pat on the back, because you are getting somewhere.
Now, I'm going to suggest that you start with the Db major scale. Most teachers -- including me, most of the time -- recommend starting with C major, because you don't have to worry about black keys and scales are confusing enough as it is. But C major is actually one of the very hardest to learn to play evenly, also because there are no black keys. From a purely physical standpoint, Db is one of the easiest scales. It falls naturally under your hands: all white keys are played with the thumb, and all black keys are played with 2, 3 or 4. So, the long keys are played with the short finger (i.e. your thumb) and the short keys are played with the longer fingers. (Also, working on a scale with no black keys doesn't address the specific problem that you are mentioning.)
Start with two octaves. Play slowly -- VERY slowly. Slowly enough that you can say to yourself as you go, "Ok, next note. Two in left hand, four in right. Ok, next note. Thumb in both hands, playing C." (m.m. 40 per note is probably about where I'd start, but you can start slower.) If a finger slips off of a key, go back two or three notes, figure out why, and try again.
The more conscientious you are about addressing the problem, the more quickly you will get rid of it. (The computer maxim "garbage in, garbage out" applies equally well to piano practice, I'm afraid. Keep that in mind.)
Gradually add in three octaves and then four; gradually add in other scales. Your goal is to learn all 36 of them, in four octaves, four notes to a beat, m.m. 120. (That was the standard for music majors whose major instrument wasn't piano. Piano majors had to get them up to at least 144.)
You will find that scale study addresses all sorts of deficiencies in your technique, as you work with them. This is why they are considered essential by most of the top pianists. Good luck! And persevere.
Keyboard players don't use anything to "give them some grip", so don't try.
We can't actually see what you are doing, so it's hard to diagnose what the problem is. I would guess your hand position is wrong. Fingers on the white keys should be close to the ends of the black keys, except for your thumb and pinky, and your fingers should not be "flat" but curved.
In fact going back a step from this, your sitting position may be wrong which means your hands don't "naturally" take the correct position.
Look on YouTube for "piano posture" - there are many videos showing what it should be like.
You haven't taken HS physics yet? Every motion has an equal and opposite motion. If you have been trained to depress the keys with the weight of the arm or, gravity, then you know in order to play down you must first "play up."
Like swinging a bat, you must backswing first; walk forward, push backward; cast a fishing pole-punch someone-swing a tennis racquet-kick a ball . . . they all have equal and OPPOSITE motions.
The piano is in front, away from you so you have to constantly have a forward shift to your arm. If you haven't noticed, your fingers are all a different length which requires you to have an in/out motion to make them the same "length." If you play from a static, still position, you will fall off the keys. If you try to equalize your fingers in a claw position you will fall off the keys.
Your hand wants to place the finger straight down on the key but our tendency is to retract so you need a constant "shape" to your arm to keep playing forward.
You need to get your playing in your arm. Specifically your pronator and supinator muscles. And gravity. Your fingers have no muscle and to play from the fingers will strain your long flexor tendons. Don't do that.
You may have to find a new teacher for your present one will cripple you in years to come.