I must say, as confusing as the SLRs were to a newby, the lens are much worse. I guess it will get easier with familiarity.
The D5000 came with the Nikon DX AF-S Nikkor 18-55mm 3.5-5.6 G. so that seems to qualify for what you mentioned.
The Sigma I had thought was the 1.8f you mentioned. The apparently had a wide angle lens and one with macro.The one offerred was much cheaper than any i found, so rather suspicious.
Turns out it is 28mm f2.8 I think - when you google it, there are some listed, and it is a very inexpensive lens. Maybe very old also, as not listed on Sigma or many other places.
You mentioned "A supplementary close-up lens may be another, equally inexpensive, option." I am not sure what this is - different than macro? I had been looking at perhaps the Tamron 90mm Macro, which gets very good reviews, and is about 450.