Best Budget Lens for Nikon DSLRs

Hi I am very new in this group, but I am a regular visitor of DPREVIEW.

Straight to the topic, i bought my new DSLR Nikon D7000, now i own Nikkor 70-300 AF-S lens mainly for my outside "bird on the tree" photography and 50mm 1.8G which am using for portraits and background blur both inside and outdoor photography, I am a photography hobbyist and i wish to explore more in photography. I want to know you opinion about some best lens from nikon/sigma/tamron, which i can use in my Nikon d7000 and also later in my full frame FX dream camera too, Nikkor 105mm macro is there in my wish list, tell your suggestions about a good, also ofcouse budget lens for..
1. Low light wildlife photography, because my Nikkor 70-300 will die after 5 or 6PM some time after 4pm in cloudy days
2. For shooting landscapes and wide angle shots
3. Good Micros, if you have any good alternative Nikkor 105mm

Thanks!

Sree Nair