If you're a first timer, I highly suggest Kobold Berserker. It is really simple, really easy, and great for getting a first win. Here's how it works.
1) Press "m" and turn off training Armour. You're going to be a DEX fighter.
2) While I'm on skills, hang on to that mace you start with, no matter how un-Koboldish it seems. Turn off the Maces and Flails skill at level 12. I'll explain why later.
3) Kill stuff, and butcher and eat everything that's not poisonous, mutagenic, or rotting until you get to Engorged.
4) Sacrifice all the corpses you can't eat.
5) Abuse Trog's invocations. Use Berserk when you need a serious edge against an enemy, Trog's Hand for good healing through regeneration, and Brothers in Arms in the mid-game to pretty much kill everything. But don't use BiA too much, because you need piety.
6) Why do you need piety? Well, when you become Trog's Champion, he'll shower you with gifts of dubious quality. Having specialized in Maces and Flails, Trog will hand you a demon whip - and I swear, it is one of the best weapons in the game. I got one very early and I brutalized the whole game with it- it was my first and only win, although right now I have a decent spellcaster who's coming close.
7) Tackle the game in this order - Dungeon to the Lair of Beasts -> All of the Lair (Orc will probably come first in the Dungeon, but Lair is far easier) -> The Orcish Mines (Do not go into the Elven Halls, it will be a deathtrap at your level) -> The FIRST FOUR floors of the Swamp/Shoals/Snake (The fifth floor is the last level - a branch end - and it will be the hardest. Also ignore the Slime Pits because that place is a deathtrap.) -> The Dungeon up to the Vaults -> The FIRST SEVEN floors of the Vaults (The eighth floor is one of the toughest areas in the game in a standard run) -> The FIRST FOUR floors of the Elven Halls (You're probably sensing a pattern
) -> The rest of the Dungeon -> The branch ends of Swamp/Shoals/Snake (For the runes there which are Macguffins needed to enter the final zone of the standard game.) -> The branch end of the Elven Halls (Can be skipped, as it has no rune and can be very dangerous, but it had good loot.) -> The branch end of the Vaults (There is an ambush of a ton of vault guards when you enter - take them slowly and lure them up the stairs, don't be a hero and fight them all at once. This is actually a very important Crawl strategy you should heavily abuse over the course of the whole game to survive.) -> Zot (Make sure you have good fire resistance - at least two levels - electricity resistance, and mutation resistance. The orbs of fire in Zot are the nastiest things you will fight throughout the entirety of the game, with a possible exception for the ancient liches also found in Zot, and fire and mutation resistance can neutralize much of their danger, although far from all. The electricity resistance is for the electric golems which are incredibly dangerous, although they may not appear to be so at first.) -> Grab the Orb -> Run back to the entrance, and win!
Yeah, that was probably way longer than it needed to be, but seriously, this is how you win a KoBe, speaking from experience