It's been said, but in general - clean new strings as opposed to a specific brand. A brand may give you the sound of clean strings for longer.
I prefer Dean Markley Blue Steels although I do end up changing them a lot. Ernie Balls seem to die off fairly quickly, but are cheap. D'Addarios seems like a good compromise. Never liked the Elixirs. DR Black Beauties looked cool, but didn't last.
Either go for nice strings are restring half the time or go for "standard" strings which are more affordable and string more often.
Prevail: I find that a little too with DM Blue Steels. Stretching them after fitting and retuning solves that problem :-D