All lens and converters are suitable for D80 as long as it is Nikon mount. Are you talking about macro or normal lens? what do you intent to capture and how much do you willing to spend? Be specified else very hard to tell.
i5htar, I'm also another newbie who loves to take pics of insects.
Used to do it with my compact camera, but lately just bought a D90 to upgrade.
Hope it won't be too silly to ask this, but how big the insects you would like to take pictures off and how close up you want to take them?
Recently, I have tried using the 18-105mm kit lens that comes with D90 to try to take pictures of some really really small ants at home on the kitchen table to test its capabilities.
Of course cannot take so close until can see the ants' compound eyes lah.
But I can take them from a distance of ~15cm using the macro mode.
This was what the camera saw of the small ants:
These are after I zoomed into the picture and cropped: