Well if you're just planning on using Darkness Howl, then a dark-type starter is what you need. All the suggestions (aside from Cleffa/Stantler) seem sound.
Absol Prime, Sableye, Sneasel... I like Absol Prime the best. It helps get more damage on your opponent's Pokemon and its attack isn't too bad. I'd try to run 3 or 4 of them.