@KAISER S0ZE the addition of spell fragments both increases the maximum effect, and the likelyhood of the maximum effect being applied. Compare left (zero spell frags, 40% max effect, 0% critical effect chance), with right (1000 spell frags, 46.3% max effect, 3.2% critical effect chance).
The percentage chance for each effect increases with each added ingredient, but changes as you mix in other ingredients as they have their own percentage chances. Thus, you'd get the highest chance of single effect if you only apply the ingredient with the highest chance multiple times, but the Witch Point costs increase much more than if mixing ingredients. The diamond costs however stays the same, always 25 diamonds.
Compare; one Ear Truffle, 7.% chance of seeds, 20% success rate, two ear Truffles, 10.6% chance of seeds, 28% success rate.
There are several fighting potions, but for example the Generals Mayhem, which increases Strength of all Barracks Units, has the highest chance of effect using Mana Shells, at 5.5% for the first ingredient. I will post an overview later today.