I like Andre_Hardings advice. I also feel that you should concentrate on KP openings and only play QP Openings as Black, when White can obviously force them on you.
The Great Czech GM Richard Reti in his classic book "Masters of the ChessBoard" also advises beginners and novices to play open games ie Double KP Openings whenever possible and not even play single KP Openings until they begin to learn the Double KP lines.
Finally I advise you to refrain from buying specialized opening books (ie on the London System or whatever) until your rating goes up several hundred pts. In the meantime MCO-15 and/or NCO (Nunns Chess Openings) would be excellent "one-volume opening encyclopedia(s)" for you. You should also read 1 or 2 works about opening theory in general before buying specialized works IMHO, such as GM Fine's Ideas Behind The Chess Openings or something more up-to-date.
Personally, I like cookie-cutter systems, especially the London and the Giouco Pianissimo. They don't require much theory to learn, there's little risk, and you know exactly what you're getting yourself into.
A few years ago, I watched a video lecture where a GM suggested using these opening systems for "just playing chess, no muck or fuss". I couldn't agree more.