My advice would be sticking to only Ruby and maybe Diamond in lower level.
Main reason is simply the expensive refill. Each alchemy stone that you have active while farming is an additional ~4-5kk / hour expense (1/4 of a Time Elixir (M)). Also, in lower level it really is not necessary to have any alchemy, so the small value you get from let's say 5 crit in jade or 3 mob in garnet does not warrant the high amount of refill costs in my eyes.
So, my personal advice:
First, go for a CL1 ruby avg / atk when you can afford it and don't have other big priorities. Then, stick with it for a while.
Maybe get a diamond, it is debatable if the extra dmg is worth it, but it is reasonable.
Once you get to red forest, an argument can be made for a garnet, since as a warrior, it can be rather tough, and the garnet has the perfect red forest kit: Hp + earth res + magic res + mob.
So, a garnet for red forest - while not necessary with the right equip - is still a reasonable investment.
Once you then push to beta (lv90 maps), the gamechanger alchemy is onyx, as you can get pierce resistance (and arrow dodge) on there. Pierce resistance here is the important bonus, which helps a ton at the metins there.
And later on, mainly for runs, you can invest into jade for hp and a bit more dmg from crit, or a sapphire with bosses (or a diamond if you didnt get one before).