Jorge,
Sorry for the delayed reply. Every time I had one typed up my ipad would auto-refresh the page as I grabbed links, erasing what I'd typed up. Sooo...we're on the pc now....
Looking about there doesn't seem to be many 3rd party options on lenses for your g5 (this is more so a lumix line thing). From some searching, it seems tamron and sigma are in the works of making lenses for mirrorless systems.
Backtracking a little, for a cheaper side of things I'd look into a Gary Fong type flash diffuser. These and similar products should be accurately white as to not throw off the white balance of the flash itself. You can somewhat see this in your above photo with how the paper towel is pink! B&H Photo is your friend for just about anything photography wise, as is Adorama. Both of these are in NY though and I'm not familiar with what quality photo/video stores in your area.
The next 2 things I'd look into are a decent prime lens and an external flash. I shoot with Nikon equipment. I started with a lowly little Nikon Coolpix 4500, graduated to a D70 in 2004 and stepped up to a D300 in 2008. Two of the best pieces of advice I got when I made the plunge into DSLR was shooting in aperture priority (this allows you to control how much or how little is in focus, but at the price of shutter speed at times) and investing in a quality macro lens. The lens I went with was the Nikon Nkikor 60mm ƒ/2.8 and it spends about 90% of the time on the front of my D300.
The next thing that helped me was an external flash, allowing me to get lighting off body and illuminating where I wanted/needed it. The setup I use now for the photos I've posted here of my corns consists of a homemade softbox, my D300, an SB-800 and an SB-600 flashes firing wirelessly. My first shot before I start taking photos of actual subjects is a photo of a
WhiBal White Balance Reference Card. This card is a "digital" version of an old school neutral gray card. The first reference photo I load up into photoshop, allowing me to set my gray, white, and blacks points, save that profile, and then load it into images of subjects taken under that lighting. The idea is to get as accurate as possible of color representation of the animal/photographic subject under those set lighting conditions.
In your case, I'd look into the
Leica 45mm ƒ/2.8 micro lens and either the
DMW-FL360L or DMW-FL500 flashes.
