I think I have got an idea/theory on how you can get 'Great effort' or 'Amazing effort'.
I'm not 100% sure, but I think you need to do the following:
- Once you get to the training, you see your Magikarp at first train in a slow pace.
- If you tap once, you'll notice it goes faster.
- Here comes the tricky part, because the time it trains in a fast pace is about two seconds, until it fades out.
I think what you need to try to do is tap the exact moment it begins to fade out, you get a better chance of a 'great' or 'amazing' effort.
I have no idea if it is true, but it something I have been experimenting and I get the idea it does get me results...
Nevermind it, I don't think it is possible.