I've read all of the above posts and agree with about 95% of the advice, personally I am a Nikon guy as that's what I started with and I've just added kit as I've gone along, it all works well for me. I am still DSLR rather than full frame as, for the type of work I do, I don't see a massive advantage in swapping all kit and lenses although that may change going forward. I love that you have been bitten by the bug, just go with the best body you can afford (given your budget a D7100 maybe) plus a couple of lenses, maybe given your stated interests I would say a wide angle (maybe 12-24mm or similar), and a prime is also a good shout (50mm f1.4 is my choice especially for gigs). A bit of quick advice from me is to save some of your budget for editing software, I have the Adobe plan which includes lightroom and photoshop for a tenner a month and it is brilliant for me given I use it every day, it's literally the price of three pints a month and will elevate your photography massively.
MPB gets a big thumbs up from me also, I have bought, sold and traded kit on there with 100% satisfaction.
Hey, just get out there and enjoy it, remember that composition is 90% of a good image, the other 10% is lighting, make it interesting and maybe a bit different from the 'norm'. Enjoy fella, feel free to shout me if I can help with anything, cheers, Ian.