Just to clarify a bit here, I'm talking eng mixer, wireless, and shotgun. I mostly work with older guys with older gear and I'm sure in the digital tx/rx age things are changing rapidly and drastically.
There's no way to know what wireless frequencies will be open to us in the future. As it stands right now, the future is up in the air, and anyone who tells you what frequencies are safe is just making guesses.
As far as gear goes, I agree with Rodney. Sound Devices 552 is the best way to go, mixer wise. If you can't afford Lectrosonics wireless, you can get away with Sennheiser G3's. Sanken COS-11 lavs and a Sanken CS3e shotgun.
You can't get into location audio inexpensively. The minimum investment for a basic kit will cost you over $10k.