This is how I leveled alchemy 1-50 in only 1 day...
lvl 1-10: leveled by completing synthesis and log book
10-20: used a few leve quests as well as more log book
20-25: Do level 20 level 11~12 times
25-45: Do level 25 repeatable level 50 times (8 stacks of HQ hi-potions)
45-50: Do level 45 leve 10 times (1.5 stacks)
I saved up 80 leves before I started. Also, buying the HQ stacks on my legacy server cost around 200k (directly from the crafter), however I did make that money back from the leves and from selling the leftovers on the market board at the going value.
If you shout in mor dhona, you should be able to buy the stacks cheaper, since it is a guaranteed sell for the crafters.