To start, I know how you feel about dying in a lab by the green potions. I lost a 7/8 rogue to one a week or two ago. Still salty about it.
A common guide is to make a wizard and run only sprite worlds with it, but I find this annoying and monotonous since I suck a$$ at playing wizard.
Everyone has their own way to rebuild and get better, so here's mine:
(I'd like to mention I always keep some backup items/pots in my vault just in case I need them.)
As stated above, get a class that suits you. For me it's a melee class or an archer. Choose your class, and level it up. At level 20, spend 2-3 def to buy a mid-tier set for it. Worst case, ask Blubber or myself and we can donate items.
Depending on the class, I recommend you do different things:
~For staff classes, run UDLs, sprites, and snake pits. You can also farm the godlands pretty easily with these guys, and wizard has a higher chance for pot drops in the glands than other classes.
~For melee classes, run UDLs, sprites, snake pits, cemeteries, and abysses/sewers if you're capable.
~For dagger classes, run UDLs, sprites, snake pits, cemeteries.
~Wand classes suck. Don't play them.
I'm kidding. xD
For wand classes, just run the typical stuff (sprites ,UDLs ,snake pits).
This is assuming you're 0/8, no pots drunk, w/mid-tier items.
When you get pots;
~If you have 2+ character slots, max the second character AND DON'T USE IT UNTIL IT'S MAXED!
~Store extra pots in your vault/on mules. Put nothing into the farming character.
~If you have 1 character slot, keep gathering pots and trading them for more expensive ones, keeping life on mules or in your vault.
~When you have enough pots stored up, do the math and see how far you can max a character with what you have.
Please note that if you're efficient you can get a mana to a life just from sprite worlds in about 30 minutes.
Remember, if you have questions, PM me here and I'd be happy to help farm with you. Good luck!