Roll for your character at home. The characters could have a total of 75 points among their ability scores. If you were a slight bit above the 75 points, then you could decrease one ability score by two points and raise another one by one point in order to modify your rolled character slightly. Gold is the default amount for third level as stated in the DMG, namely 2,700 gps. Starting XP will be 5,250 XP, just shy of fourth level.
Books used are the core, however I would be willing to allow elements outside the core books depending on a case by case basis, such as when we had a kobold rogue.
The first post in this thread gives some background on the campaign world. Because the group is currently in the dwarven kingdom of Bermax, trapped with some Dorinthian refugees they came to rescue, and blockaded by Imperial troops, here are some character ideas by race:
Humans, halfling, and half-elves: These will most likely come from the group of refugees rescued. He may be anyone from an experienced soldier with a peasant background to a noble enlisted as a paladin or even an aloof wandering monk exploring the world away from his monastary, when he falls in with the plight of the refugees. Also, it may be possible that a human or half-elf might be serving in the Imperial army and decide for one reason or another to defect or perhaps that the Dorinthian cause is their own.
Dwarves: This one is easy, since you are currently inside the kingdom. Most dwarves will be fighters, rogues, or clerics in the kingdom, although other rarer classes are possible. A barbarian, ranger, druid, or monk dwarf will be a strange oddity and most likely have come from outside to warn the kingdom of the impending danger from the invading Imperials.
Gnomes: A gnome is likely to be a part of an ambassadorial delegation visiting the dwarven community at the time of invasion. They are likely to be of any class, except barbarian, druid, ranger, and monk, which would probably come from outside the community.
Elf: An elf would be rare in this case, although it is conceivable that one with a reason to wander far from the elven lands may have sought refuge from the Imperials among the dwarves. Classes such as druid, ranger, rogue, and monk would be the likely candidates. A barbarian would be extremely rare and tricky to explain away.
Half-Orc: This would be even more difficult to explain away because of how hard it is that he would survive this far, unless the character is a non-evil wanderer, such as a barbarian, ranger, or monk. Also, half-orcs were known in Dorinthian areas that suffered from orc invasions a generation ago, usually on the frontier borders of the country. So theoretically, a half-orc may have enlisted in the military before the final Dorinthian defeats and became a part of these refugees that come from various cities in the center and of what was once Dorinthia. Such a half-orc could be a more professional class, such as a fighter or paladin.