Question: First of all I just started doing barre chords after learning ordinary non-barre chords. Problem is they don't sound so well, so my question is, will training with hand grippers help me achieve this? Because I've been applying equal pressure and they still sound a bit off, only a bit off.

Answer: 
It turns out that strength is not what is needed to improve your ability to finger barre chords, or any chords. It's mostly about precise placement and using the minimum amount of force to hold it down.

It's not necessarily that equal pressure is correct. You just need the right amount of pressure for each fret and string.
I don't find those hand-grippers very effective in teaching you how to make your barre chords sound better. The truth is, a large part of getting your barre chords to sound good comes from good technique. There are quite a number of tiny details that will help you achieve a good sounding barre chord with minimal effort. Many people think that in order to get your barre chords down, you need quite a lot of strength, and that is not true at all. Remember that precision beats power. Focus on getting the details of the technique correct. 

Another thing that may be preventing you from getting your barre chords down is your guitar's set up. If your strings are too far away from the fretboard, you're going to have a really tough time getting your chords to sound good. Make sure your guitar is properly set up.