I would save your money until you know that you need a particular lens. Modern Zooms are so good on digital cameras that a vast majority of people can not see any difference at all in sharpness. However longer focal length and wider apertures allow you to throw the back ground out of focus more easily than shorter focal lengths and smaller apertures. Moderate telephotos like a 90 or 135mm on full frame give more pleasing and natural drawing of the Features in portraits. But zooms in this range do equally well if the Aperture range is also suitable. Which on entry level Zooms may not be the case, especially if you want the backgrounds to be soft. On an Aps camera a 50mm or thereabouts wide aperture lens F1.4 or so makes a very good small studio portrait lens. However I find that my Fuji 18-55 f2.8-f4 zoom serves very well indeed, and is fully usable wide open. For the time being I would use what you have to see if it serves well enough, I hate to have lenses that I never get round to using, just sitting there.