Hi Nushie
If you dont own a tripod I would put the money towards that. Especially for portrait and landscape shots. Later you may want to get a better flash also. The prime lens has the advantage in lower light and the pictures will be sharper but for landscapes the kit lens you have will be better. Also the kit lens zoom in and out, so better in that you dont have to change lenses all the time and you can use it for portraits also. I think use the one you have to practice lots first. On a side note the sensor in your camera is also known as a crop sensor and is smaller than a full frame. What that means is that the 50mm lens fitted to your camera will actually be about 75mm.
Hope that helps <img src='http://www.dolforums.com.au/public/style_emoticons/<#EMO_DIR#>/biggrin.gif' class='bbc_emoticon' alt=':D' />