For beginners we recommend Phosphor Bronze strings, light or extra light gauge.
e.g. Rotosound JK11 - Jumbo Kings are Rotosound's best selling acoustic string. Phosphor Bronze wound Acoustic Guitar strings with superb warm tone, clarity and sustain. Favoured by such artists as John Renbourn, Bob Geldof and Gordon Giltrap.

JK11 have string gauges of: .011 .015 .022w .030 .042 .052

Lighter strings are easier to fret for beginners, but are more susceptible to fret buzz and have a thinner sound.