I don’t think you’ll go far wrong using sRGB. In order to benefit from Adobe RGB’s wider gamut, everything that processes the image (windows, monitor, image editing applications, printer, printing device etc) must be correctly setup to use Adobe RGB. This is often not the case so Adobe RGB images appear dull. sRGB is far more standard and the best choice for amateur photography.
Remember though that sRGB is a standard colour space (a way of referring to colours) and does not necessarily mean that your device (e.g. monitor) is accurately reproducing them. For this you need to calibrate your monitor using devices such as Datacolor’s Spyder system.