Unlimited spell ingredients.
When you get down to the last measure of one of your spell ingredients you can use what seems like a bug in the game to get an unlimited amount of measures for that ingredient.
Once you put the last drop of a potion into your lab equipment and just as the droplet hits the bowl, you quickly click on the potion rack and instead of the potion disappearing it reappears on your cursor. You then add another drop to the mixture and the amount left starts going into the minus figures and it never runs out. Make sure you don't try and put the ingredient back down on the rack straight away because it will disappear.
Your timing has to be perfect however. As soon as the drop hits the bowl you must simultaneously click the mouse on the ingredient rack. It may take a little practice but you will eventually get the hang of it and have a rack full of everlasting ingredients to experiment with.
When the ingredient salesman calls you just need to buy one measure of each ingredient that you don't have and do the above trick.
These are the main set of spells that I used to max out my dragons' stats. A couple of the ingredients need to be bought from a trader as you don't start the game with them. This may not be the most efficient way but it worked for me. Some of the spells may need to be cast 2 or 3 times to get the maximum effect.
Dragon Health Rasgon grind & heat x 2 (Director) Oreganse normal & heat x 3 (Affector)
Dragon Strength Rasgon grind & heat x 2 (Director) Ulin normal & condense x 3 (Affector) Pfoss normal and heat x 1 (Power)
Dragon Speed Rasgon grind & heat x 2 (Director) Arolig normal & condense x 6 (Affector) Pfoss normal and heat x 4 (Power) (after this health and strength are slightly down and eyesight and wisdom are down)
Eyesight Rasgon grind & heat x 2 (Director) Igele normal & condense x 6 (Affector) Pfoss normal and heat x 5 (Power) (after this speed is slightly down)
Wisdom Rasgon grind & heat x 2 (Director) Haloros cutting x 4 (Affector) Pfoss normal and heat x 1 (Power) (health and strength should be back up to maximum)
Speed again Rasgon grind & heat x 2 (Director) arolig grind & heat x 3 (Affector) Pfoss normal and heat x 2 (Power) (health will be a tiny bit lower than maximum at this point)
An alternative to using Pfoss to increase the spell power is to use Acrus with mixing and heating, but you'll have to figure out how much you can add without your equipment blowing up.