I would add the 35mm f/1.8 DX G and the 50mm f/1.8 G lenses. You want a lens for walking around with friends and around the campfire - the 35mm. For portrait shots at the photography course at the studio the 50mm. That stays in your budget, gives you a faster lens option over the zooms, sharp enough for most needs. I would start by just picking up one of the two. You need to use it long enough so you know ahead of time where the person needs to be and where you need to be so you can frame the image how you want. You can try this out now by just setting your zoom lens and not touching the zoom ring the rest of the day, use your feet (and dream about the extra three stops of light). Another option, pick up a Nikon SB-700 flash unit, its in the budget, and going with bounce or off camera flash will fix any issues with low light and the kit lens. It will also work great in Commander mode with the D90.