I have just come back to this server and Ragnarok too, and have decided that I should challenge myself and play something I always fancied but never got around to, and the Alchemist is the first.
Unfortunately, I have no idea what to do, how to play one, create one, etc.
Any help would be greatly appreciated. Are they fun to play, how do you play them, etc.
Alchemists aren't expensive at all; Creators are (either in terms of time or zeny, depending on which route you go).
As an alchemist you have a bunch of choices. You can level like a STR/AGI melee type and wait until you can flee things (and once you're an alchemist get a homunculus to help you kill). Or you can go STR/VIT and just pot spam through damage (and once you're an alchemist get a homunculus to help you kill). Or you could get your hands on a fireblend/ice falchion and bolt things to level from level 40 onwards (and once you're an alchemist get a homunculus to do the base level work for you).
Either way, once you're an alchemist you'll want to get a homunculus as soon as possible. I suggest vanilmirth for leveling, they have the overall best stat growth in every base stat. But, basically, you can play an alchemist like any melee class (admittedly a relatively weak melee class) or you can play it like a mage class (admittedly a really weak mage class).
It's fairly slow leveling until your homunculus can leech you and then you'll need to find some way to gain job levels (but that's not too hard once you're higher leveled). Best of luck!