A great big part of a character is background. Most folks won't know everything about everything when they first start, so keep it simple. There's a list of possible occupations and what they are on the occupations page.

There is far more to life in the campaign than the hard-coded guilds. A lot of these require imagination and basically 'pretending', but it doesn't have to be hard-coded for you to do it.

If you're a basket-weaver, pretend to make baskets and buy the materials for them. Then hock the baskets in the marketplace to people who walk by.

Example:
(Note, no one in the following example actually has a basket)

The stern, black-haired man arrives from the east.

The skeletal, half-elven man looks up at the stern, black-haired man as 
he enters.

The stern, black-haired man frowns at the skeletal, half-elven man.

the skeletal, half-elven man says, in sirihish:
	"Baskets, sir.  The finest baskets in the city-state."

the skeletal, half-elven man nods several times to himself.

the stern, black-haired man looks down at the skeletal, half-elven man.

the skeletal, half-elven man says, in sirihish:
	"The best.  You not be disappointed.  Fair price, too.  Only 45 
obsidian for basket that will last you all your life!"

Holding up a thickly-woven leather and grass basket, the skeletal, 
half-elven man says, to the stern, black-haired man, in sirihish:
	"You could use basket, no?  Handy to carry arrows in.  For lady 
while she shops?"

the skeletal, half-elven man grins a gap-toothed and blackened smile, 
bobbing his head at a richly-dressed woman as she walks by.

Tossing a small handful of coins at the half-elf, the stern, black-haired 
man says, in sirihish:
     "Keep your baskets, half-breed.  Now out of my sight."

the stern, black-haired man gives a small handful of coins to the 
skeletal, half-elven man.

Meanwhile, the half-elf could have the hard-coded guild of merchant and use his place in the market to eavesdrop on people.

Someone once said that your actual in-character occupation is what your PC is doing when you're not logged in. Use it as flavor for your character while you're adventuring.

Don't go around telling people that you're a warrior or a ranger or a burglar. Use something else to flavor it. Be an outrider or a bounty-hunter. Be a mercenary or a slave-handler. Be a fortune-teller or a gambler. It adds flavor to the game, and sometimes it's fun to stretch your imagination to break traditional roles.

Remember, you can earn a living just from making up good stories in the theme and telling them in the inn.

Also, it's tempting to make 'the badass' character and go out and be the superhero of all superheros. But don't turn up your nose at playing the simple slave.

Remember, there are a lot of people out there who can play a good badass and beat the hell out of things, but there are very few people who play a good slave or bard.

Getting into the politics around your master or of the city in general can be very interesting, too. Don't limit yourself. There's nothing keeping you from seeing things and doing things. Be creative.