The main areas of spending within the parks are food/drink and souvenirs. Obviously souvenirs are not compulsory but most of us will be inclined to pick up at least one or two :-)
Food and Drink
That phrase is usually delivered that way round but Florida is often hot, which increases the need for drinks and seems to reduce appetite in many people, so drink is often more of a priority.
Drinks
Most drinks in the Disney parks will start at a little above $2. Other than kids' meals, ' Combo' type meals in the parks don't include a drink.
$2 doesn't seem like much, but if there are four of you and you need 3 drinks a day each ( that may well be on the low side) then you could be spending upwards of $24 ( around £16 ) a day on drinks alone .
Remember that while sweetened drinks may taste nice they often seem less refreshing than plain water.
There are drinking fountains throughout all the Disney parks. Some people have hygiene concerns, the fountains seem ok to me :-) Some people also feel that the water in the parks has a distinctive taste that they dislike. Carrying a water bottle with a 'brita' style filter fitted can minimise the taste. However the bottles are not always easy to buy, have an initial purchase cost and have to be permanently carried.
If you would prefer, most counter services / refreshment carts in the Disney parks are happy to give you a cup of iced tap water for free. Small packets of dissolvable crystals for drinks eg crystal lite can be purchased at most US supermarkets. They are light, relatively inexpensive and come in a range of flavours that some people feel make the water more palatable.
Food
Bringing Your Own Food In
It is perfectly acceptable to take packed food into the park. In this context Disney's rules forbid only alcohol, glass, coolers with wheels and very large coolers. Bag check staff often seem to view packed food only as an opportunity for a joke and may smilingly request a lunch invite.
Packing food can not only save money but can ensure a better variety ,of healthier food, more precisely tailored to the needs and preferences of your group. It can also be a great time saver. Lines for food can be lengthy in the parks. It can sometimes be convenient to be carrying something to eat while waiting for a ride / parade/show etc where that is permitted.
It's important to decide carefully what food to pack as foods that could become unhealthy, melted or squashed may need to be avoided. Crackers , granola bars, jerky, trail mix, dried fruit, apples can all travel well . Coolers and freezer packs increase the possibilities enormously.
Something that may help kids view packed food as more of a 'treat' is incorporating any favourite snack that may be restricted at home. Many of us have colourful or character themed disposable tableware and paper napkins left over from kids parties and this can also increase kid appeal. I have even been known to include a few stickers or other tiny trinket for a DIY 'happy meal' effect.
Unless you have a stroller, carrying packed food around can be an issue. Lockers are available within each park. Costs start at around $5 plus deposit for the smaller size which obviously reduces savings. It can be a pain to have to walk back to the locker from some distant part of the park to collect your lunch. Another alternative is to give each member of the party their own food in a small back pack which shouldn't impede their enjoyment of the rides.
When you want to sit down to eat your packed food (taking a break in a hectic park day is much to be advised) then you may need to nab a nearby bench, Disney does not provide picnic areas except in the water parks and in Animal Kingdom where visitors can purchase a picnic in the park.
Some people may choose to make use of nearby counter service seating, often outside. I have never seen a sign forbidding this, although it can be a heated topic of debate on Disney discussion boards. Personally I can't see it as an issue at quiet times but your mileage may vary.
A compromise which can salve the conscience and vary the offering is to purchase a side order of fries etc at the counter service to accompany your packed food, perhaps while requesting iced tap water :-) Some people would then choose to sit indoors where they could relax in the air conditioning and enjoy any theming such as the animated entertainment at Cosmic Rays.
Table Service
With a few exceptions, such as The Pepper Market at Coronado Springs, there are largely two types of dining facility at WDW . The first option is table service, also known as full service, where a server will take your order, bring drinks etc .The second is counter service, also sometimes referred to as quick service, where you need to walk up and order.
Table service tends to be expensive but is often considered worth it because of the theming, character interaction or menu available.
There are limited options for saving, attend for breakfast or lunch where available rather than dinner, choose an appetiser rather than an entree, share an entree, stick to tap water as a drink.
Sadly, none of these will help you at the character buffets, although some visitors have reported good value in some venues when attending at a change over time eg a very late breakfast bookng may mean that lunch choices are also becoming available at the time.
Best value buffet dining at WDW has traditionally been at Trails End at Fort Wilderness. Dinner is $21 for a an adult and £12 for a child, there is a soup/salad bar only option available although I have no idea of the pricing. However it doesn't have characters and while we really enjoyed our only visit in 2005 I have read recent reports of a decline in variety / quality.
Although, in my opinion, rarely wonderful, counter service is obviously considerably less expensive, think approximately $7 - $10 plus a drink for an adult and $5 including a drink for a kids meal.
Where a menu item is listed with a side that you don't require, it is usually possible to order it without and the price is reduced accordingly.
Some counter service meals my be considered large enough for sharing.At Cosmic Ray's in Magic Kingdoma the half rotisserie chicken and barbecue rib with mashed potato and seasonal vegetable can make a nice change from fried options. It costs around $14 but could be split between two, maybe more if light eaters.
Where a menu offers a 'double' burger it is often possible to purchase a second bun for a minimal fee and make two burgers out of it. This works particularly well at places like Pecos Bills and Cosmic Rays in Magic Kingdom where there is a fixings bar that can be added to the burgers or used to make a side sald type accompaniment.
At counter service there is no difficulty in ordering a child's meal for an adult, which may work particularly well fo those who dislike other methods of acquiring drinks inexpensively. Obviously kids meals are small but as mentioned before Florida heat diminishes appetite in many people and a smaller meal may free up space and money for a 'treat' later.
The children's meals have altered in the last few years to take on a more 'healthy' focus. Opinions on them are mixed. However it's worth knowing that many places will substitute the set drinks and sides for soda and fries if requested to.
I particularly like the places where the kids choices are a reflection of the adult menu. At Anandapur Local Food Cafes ( the counter service arm of Yak and Yeti restaurant in Animal Kingdom) a childs pork roll meal with a double side of chicken fried rice and milk, water or juice could seem pretty appealing for $5 .