It depends how old you want your alchemist to be when you start adventuring...
In all cases I prefer starting future alchemists out as rural commoners, best start stat trio for str end and int.
20 year olds I would recommend oblate over student, because you get more alchemy points that way, but most importantly because you will not be interacting with alchemists with a 20 year old without first brewing some potions to get your skill up... Oblates come with a formula, students do not.
25 year olds have two options IMO: Oblate -> Oblate or Student -> Alchemist... Oblate -> Oblate gives you 14 points in alchemy as opposed to 15, but starts you with two formulas as opposed to one... I prefer oblates because of the reasons cited for 20 year olds, plus the fact that taking an alchemist profession knocks you a str point...
30+ Student -> Alchemist -> Master Alchemist -> ... If you start this old you're probably not counting on taking 5-10 years to really develop all your skills, so get as high an alchemy score and as many formulae as possible. Master Alchemist gives 2 formula and the most alchemy skill so its a clear winner over any oblate combo.
I know the thread is old, but its one of the newest Darklands posts...