I got the 150-500 from Sigma for long range. Great lens and more affordable.
I also started out with an inexpensive set of extension tubes for macro before saving up for a Nikon macro lens. Once you get going you will always want more! Welcome to the addiction.
I agree Go with the sigma if you buy there top of the line lens there not a dimes worth of difference between them and the Nikon lens but a big difference in price my Nature lens is the 300-800 f 5.6 they call it the Sig monster and its awesome I have taken some fantastic shots with it
That's a tough one - there are so many more options now than there were just 10 years ago. Big glass (low f stops like f/2.8 or f/4) will give you more options, focus faster, & stay in focus better than lenses with higher f stops (like f/5.6). Those lenses are also larger, heavier and more expensive. If you are REALLY into it, then one of the big primes is hard to beat (like the 400 mm f/2.8, 500 mm f/4, or 600 mm f/4), whether it is Nikon or Sigma.
There are several reasonable telephoto zoom lenses that reach out to 400 and 500 mm now, both in Nikon and Sigma brands. For every savings in length, weight, diameter, there is an offset in something (focusing speed, low light capability, etc.). Now, the advances in focus technology and camera capabilities make these newer lenses better than the best old body lens/combination of a decade or so ago - but they still don't match the capability of the best body/lens combination of today. That said, there is nothing wrong with them. I've got one (I replaced my 80-200 f/2.8 with the newest 80-400 f/5.6 after having shot a loaner & seen folks get great shots with it). I wish that I'd gotten another 80-200 f/2.8 rather than this newer lens, mostly for the low light capability (early morning in the duck blind, early evening on a food plot, and under the lights at sports events).
All that said, there are lots of options, and it really depends on what YOU want the lens to do. Borrowing/renting the lenses & trying them is the best way to go before you buy (but that still didn't keep me from making what I think of as a mistake).
There are 3 basic options for true macro lenses with a Nikon (excluding extension tubes & close-up filters): the 50-60 mm range, the 90-105 mm range, and the 200 mm. It depends on whether you go Nikon or Sigma or other brand. I've got a 60 mm macro, a 105 mm macro, and a 200 mm macro and use them all. The 60 can be a pain when photographing frogs, bugs, flowers because I have to get so close to fill the frame - that means that I scare the critter or knock the dew off the flower. The 105 works well most of the time, but in anything but bright light, when I am close to my subject, then I fight for more depth of field. The 200 mm is generally a pain in the tail because I fight for depth of field so hard, but on calm days with bright light & no wind, it is GREAT for butterflies, bees, dragonflies, etc. I'd say try the 60 and 105 mm and see which fits your style of shooting best (and either of those makes a great portrait lens as well).