iTTL is very nifty, you can throw your flash on that setting and it will (in most cases) automatically set the flash to the correct power setting. It's very clever and I can't even begin to understand it. I use it for macro photography and it hasn't failed me yet. Worth having if you'll be in a situation where you can't or don't want to constantly fiddle with the flash power settings to be able to expose the photo correctly. I'm assuming you will probably want/need this.
If you want a flash solely for portaits and shit where you have all the time in the world to set things up however you want, manual is fantastic. You can buy 2 or 3 of them for the same price as a good one with iTTL. I can't recommend specific models, because I haven't looked into them deeply enough. Brands that are worth a look are Yong-Nuo and Nissin. Yong-Nuo are very popular and are probably the best ones to look at if you're buying manual. It's a whole different world of photography, so be prepared for much trial and error.
A 50 1.8 is a great lens. It's horseshit indoors for anything but portraits (on a crop camera like yours and mine), but outdoors they're great. So cheap, you have to have one in your arsenal.
If you don't want to pay the bullshit Australia tax on photography equipment, I highly recommend shopping at
DWI Digital Cameras.
