Before you even begin to break even you will spend 80k. Skill 200 or so you can begin to have skill pay for itself with plat augments, until then there is alot of competition and not much people want to buy. I can think of at least 5 jewellers who currently play in the 200+ range. (Ryst, Schumf, Tressee, Aadla, I think Cristiania and maybe a few more I cant confirm atm)
Server population ave in evening 220, # of jewellers 2-3 average.
Smithing tons of competition and limited market.
Tailoring same thing but doesnt seem to be as many. Amaelia seems to be the main tailor playing atm. Griz logs in to do combines is about all it seems.
Potion Making, there seems to be several people doing this but few people who understand just how awesome a potion can be. Shaman buffs anytime, regens, AC, heals, Mana, DSs, hastes. Potions are versatile and amazing! Just underappreciated by too many.
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Things I would actually reccommend. Fletching, it is up for a revamp that is rumored to included augments for slot 4, bows. Pottery, been in the works to do more with that for awhile too. Barring those, tailoring would probably have the least competition.
Successful businesses anticipate trends and are the first ready to give the people what they want.