I've already spoiled it for myself, I watched the video:P
He's pretty easy compared to earlier fights with him, though.
<iframe width="1280" height="720" src="http://www.youtube.com/embed/o4cqQI6MZjk" frameborder="0" allowfullscreen></iframe>
And don't forget to buy the Hawkeye... It's another 100 Rupees:)
Anyway, after you've got all that stuff, don't worry about expensive items.
You don't really need to spend a lot of Rupees until you've found the sky cannon, where you need to let it repaired for 300 Rupees.
I bought it once, because I thought it would only drain your Rupees when you got hit. Turned out I was wrong.
I donated hundreds of Rupees for an item that's completely worthless:(