For a gaiwan, I would recommend ordering from http://www.funalliance.com
. They have decent quality gaiwans cheaper than you'll find on most places online.
For yixing pots, that's not quite as easy to find online. Before buying an expensive pot, it's definately a good idea to see it first to see if it is good quality. It's kind of hard to see what kind of quality a pot is just by seeing a picture of it online.
Although, I recommend buying pots from http://www.yunnansourcing.com
. They are cheap, and of decent quality. Two of my three pots came from ysllc.
The rest of the stuff will require some google searching. You can get a tray, and some other stuff from ysllc or funalliance, but shipping those things from china isn't very cheap.
Just so you know, a filter, sniffer cups, sharing pitchers, and that larger set of tools are optional. The filter isn't needed unless you prefer to use one. Sniffer cups are just personal preference. Sharing pitchers aren't needed if you're just brewing a larger cup of tea for yourself, or you have enough gongfu. And the larger set of tools is more than you need. Usually, you'll only need to use the tea scoop, and possibly tongs.