My Disney tips:
We did stay on propety, and yes, it was pricey. We stayed at the Contemporary Inn and decided that we were only doing Disney once, let's go all the way. But it was convenient to be "right there" in the middle of everything. You didn't mention if you were staying on property, but we bought breakfast food at a grocery store and had cerial, etc. in our room every day. Our room had a small fridge and a microwave, so that helped.
Get the autograph book the minute you walk into the Magic Kingdom. There is a gift shop right at the entrance, buy the one with the slip for photos and the page next to it for the signature. I was also surprised at how many of these characters don't have their own pen, so slip one into your backpack. Sometimes, the characters can appear out of nowhere, so having the book right away helps. It's a great keepsake, you won't regret it.
Book the character breakfast early. These things fill quickly and are ridiculously expensive, but worth it. Unfortunately, I did not get this advice and my kids ended up at one that was at 7:30am on the last day of our trip. They were tired, but they enjoyed the breakfast.
Throw fashion to the wind. You need comfy shoes for Disney.
It's been a few years since we went, but to give you a dollar figure, we EASILY spent at least $200 a day when we were there. But we have great memories and who knows, maybe we will go back!
Finally, do a Disney search of this mamapedia website. There have been many posts about Disney and there is soooo much good info out there!
Have a great time!