For smaller items, create a budget light box. Decent sized cardboard box. Cut out the walls and replace them with white paper. Place paper roll from the back wall of the box to floor of the box. For extra pizzazz add glass on the floor of the light box. Hot lamps on the left, right, and top of the light box. (Work lights work good for this) When shooting with your camera. Try to step back and shoot a little farther than what you would normally do. 10-15ft away vs 1ft away from the item.
A budget fix for adding more capability with your Nikon is buying some lights. ex, I have a pair of Genesis 200 light kit, it comes with reflectors/umbrellas and it can be set off with the flash from any camera. Lighting and a basic program light Lightroom will make it look like a pro.
This is a great idea. the poor boy light boxes are great for handgun sized items. I totally forgot about those - and I have two of 'em! experiment with the light box. It's cheap and easy. soft lighting is the key. that's why you use the white paper or sheets. that acts a diffuser, giving you much softer shadows.
Lightroom is good software. There are several other free packages as well that are pretty good. Either way, you'll spend more time setting up and tweaking the photos that you will actually taking the photo itself.