I bought an Anker T320 bluetooth keyboard to use with my iPad, mainly because it had such good reviews on Amazon. It's an amazingly good keyboard! It's really light - much smaller and lighter than the Apple bluetooth keyboard I was using before. It charges via mini-USB. The keystroke action is excellent. I am very happy with it. Here is my Amazon Affiliate link to the keyboard should you want to buy it: Anker® T320 Ultrathin (4mm) Wireless Bluetooth Keyboard for iOS (iPad Air, iPad Mini 2, iPad 2 / 3 / 4), Windows and Android 3.0 and above OS with Built-in lithium battery / Aluminum Body.
The past few days I've been bringing in my new WIFI-only iPad and trying to use it tethered to my iPhone 5. It's been a frustrating experience so far. I've found that it works OK when the iPad is first tethered to the iPhone, but shortly thereafter the internet connection seems to drop out on the iPad, even though the iPhone is still reporting it to be connected OK.