I agree also, your first photo shoot was a job well done. You can never stop learning with photography so dont be afraid to try different things and change settings on your camera. Try Aperture priority adjusting the F-stops to see what results you can achieve. All the best!
I agree with Cee Dhinjan posts, F2.8 is ideal for portrait work, you can buy some great Nikon lenses with f2.8 stops. You will need to work our what sort of shooting you are going to do. Do a google search in what you are really wanting then start checking prices. We have picked up lenses on E-bay before but use it with caution cheers