This is a guide on economical alchemy training. However, you should be sure to take a reality check on any materials you buy. Prices will fluctuate across realms.
As this is intended to save you money, buy only the materials you are sure you will need. If you run out, buy more. It is always more cost-effective to gather your own materials, rather than buying them. Avoid having extras, but if you do, try to sell them back on the Auction House.
Grand Master Alchemy allows 450 maximum skill, requires level 65 and 350 skill. As of Patch 3.0.8, there are no known recipes nor achievements that require an Alchemy Skill higher than 435, so you may wish to stop after transmuting the Skyflare Diamonds to save money.