I remember when I got my first DSLR a few years ago and I was so confused with all of the options/cameras/levels/and lenses!
Most cameras now adays should work well. To get the best feel for any camera I recommend borrowing friends cameras and going to the store to handle some in person. I remember walking into a camera store all set to get a Canon Rebel 3 years ago and ended up walking out with a Pentax K10d because i liked the durable feel and weather sealing (it seemed to have the build of a nikon d700!).
I've used a Canon S90, t2i, 7D, 5D, 5DII, Nikon d40, D5000, D700, D3, and Pentax Kx, K10d, and K20d and they are all different (for obvious reasons) each with its own pros and cons.
I have the most extensive use with the Pentax system so I can give some feedback in this area. The Pentax DSLRs have come a long way and traditionally received the most criticism for Slow/ inaccurate/noisy AF and poor Low light performance. The current Kx, Kr, and K5 are some of the best Low light performers of crop body DSLRS. The AF has also been substantially improved and the shutter on the K5 and K7 sound like a knife through butter....silent. Backwards compatibility of nearly all pentax glass means that those old film lenses sitting in garages have a new life in the digital age. Though their current production line of lenses doesnt compare in size to Canon or Nikon, the combination of their meticulously designed Limited lenses, DA* weather sealed lenses and old MF glass provide lots of options.
The advanced amateur DSLRs are build like tanks. Weather sealed against dust and water. I've dropped my K20d a number of times, spilled soda on it, and used it for 3 months in Costa Rica where it rains and rains and rains. I also wash it periodically which is nice since cameras get dirty/oily. The color is awesome although sometimes a little enthusiastic.
Today, buying a used camera will save you from spending a premium while still getting great performance and image quality.
I started off with a the basic 18-50mm and 70-300mm kit lenses and learned the basics before learning my style of photography and what I wanted to purchase next!
For entry level you might look into the
Canon T1i
Canon T2i
Nikon D5000
Nikon D3100
Pentax Kx~ 400-500 used 600-800 new (excellent low light)
Pentax K200d
For advanced amateur you might look into
Canon 50d
Canon 60d
Canon 7d
Nikon d90
Nikon D300
Nikon D300s
Nikon D7000
Pentax K20d
Pentax K7
Pentax K5
for macro lenses there are plenty that you could look into but the Sigma 105mm gets good reviews and has given me great results
(comes in mounts for Canon, Nikon, Pentax and i think sony)...In Pentax mount it tends to run around 250-400 depending on if its used or new. If you went with the Pentax KX id recommend either the sigma or the DA 35 macro
here are some photos with the Sigma 105 macro
Best of luck!