When you get 5 tiles of the same color it creates a gem and sometimes I can get 5 more tiles together at the same color and create two gems of that color but is that good or is it better to just have 1gem of the color and have the other Tiles at that color spread out instead of creating 2 gems of the same color
Lol, I expect that is entirely specific to the situation!
If you have the option, look at where the gems will cause damage or charge the enemy mana and make a best-guess of whether the effect will help or hinder you.
Or if it doesn’t matter, just make the prettiest fireworks!
Having 2 diamonds does not help. You have to choose one and that effectively makes the other into a normal tile.
Having a diamond and a dragon (or multiple dragons) is great! So if you have a diamond on the board already, better to make a 4-way match and make a dragon than a 5-way for a redundant diamond.
Having 2 diamonds help if they are dead tiles and you can make one ghosting to help clean up a bad board before popping them to replace the tiles without charging the enemies Mana.