The only potions that I've seen that are in demand are fire prot extended, speed II and speed extended, strength II and strength extended, and finally potion of healing II. Sadly for small time potion manufactures the shops @ spawn are much more convinient to access. All the potions I named are bing sold in the player spawn market for 20 ecodollars each. If you could offer a lower price and find a creative way to advertise I'm sure you will get a fair amour of business. Personally I would suggest making an advertising thread on the forums.
PS: please pardon any spelling/grammar errors I made, I'm typing this from my iPod.

 

If you can get the business of a pvper even if you just have a little area they can tp to that you keep stocked up with pots you could make a ton especially if you sold pots for under 10$. Every time I go to pvp I need around 23-25 potions so if every trip I made to pvp you get 250 you'd make a good amount of cash. The trick is getting the right people.

 

Yeah, if you sold the potions I mentioned beforehand for ten ecodollars or less you would have my business :D
Do you make all the pots I mentioned?

 

Yes, when you add redstone to a potion you get the extended version the adds more time on to the time that the potions last for. And when I say (for example) pot of healing II then I mean when you add glowstone dust to improve the potency of the potion.