is it better to lean 1 opening and try to master it or learn a bit of every opening?


... But Im worried the Scotch gambit isnt good in the upper ratings and can get easily exposed
Mamedov and Guseinov both play it often. And they are both strong Grandmasters. Nakamura also played it in several US Championships, as well.
So ... it's valid.

You should do both.. you should play a variety of openings and experiment until eventually settling on one. Same thing you do in school when you study a variety of things as part of general education before you specialize in something.
If you only play online there's no reason to prepare multiple lines. If you aspire to playing OTB it's another matter, you may need to mix it up more.

As soon as I played my favorite and most played opening Scotch gambit, my rating went back up from 1000 to 1200. Before I was doing a different opening which is why I lost more than 200 ratings. But Im worried the Scotch gambit isnt good in the upper ratings and can get easily exposed
What the heck are you basing that on? Your a class D club player. You can play the Scotch Gambit all the way to GM level! No offense... put unless your 6 you are not going to be a GM.... Period. Sounds like I'm being harsh.... exactly the opposite! It's NOT!!!!! the opening that makes the chess player..... but the Chess player makes the opening.
If you like the Scotch Gambit play the Scotch Gambit... the better you get, the deeper your knowledge on the Scotch will get ... lol easily exposed... No...... only if you let yourself get outplayed... typed with "rolling eyes"
Eventually .. if you play at the club level... and stick with it, get better etc... you will get known as the resident Scotch expert of your club... (and that is always a ribbon of excellence to wear... ) gutsy people will challenge your Scotch, others will avoided like the plague...
(said because of my own experience) The problem with many (including me at one time) I kept trying to get an advantage from the opening and I kept chasing that magical opening I believed was going to be the key in becoming a high rated player. I acquired a fracking library when it comes to books on openings .... Waste of money, waste of time... Pick something you like, stick with it... the more you loose with it, the more you discover/learn what not to do... the more your going to win with it on the other end...
Best of luck... and Play that Scotch ... it's a great opening!

... Pick something you like, stick with it... the more you loose with it, the more you discover/learn what not to do... the more your going to win with it on the other end...
^ This.