Here's my first attempt at creating a deck:

Cold One Knight x 3
Cold One Riders x 3
Corsairs of Ghrond x 3
Dark Riders x 3
Discipline of Khaine x 3
Harpies x 3
Shades x 3
Vile Sorceress x 3
Walking Sacrifice x 3
Malus Darkblade x 1
Mortella x 1

Altar of Khaine x 1
Cauldron of Blood x 2
Contested Village x 3
Contested Fortress x 1
Har Ganeth x 2
Mind Killer x 2

Night Raids x 2

Boar Attack x 2
Call the Blood x 3
Invoke Khaine's Wraith x 2
Lash the Prisoner! x 2
Take Captive! x 1
We Need Your Blood x 3

What can I add to make the deck more effective at winning and what cards are taking up space? I am borrowing cards from a friend to create this deck so I might have access to other cards from different sets which I do not have access to at the moment.

Get rid of the Harpies, the Boar Attacks, one of the Night Raids, the Altar and the Contested Fortress. Add three Warpstone Excavations. Your deck will be immediately faster. Maybe not better, but definitely faster. If you have Slave Pens, consider getting rid of some of your other supports to add them.

Add Black Dragon Riders and the Wight Lord for some good fightin' power. Or the Enraged Varghuff .