The theme parks want you to spend your entire trip visiting THEM (and not their competitors) so they provide you lots of incentive to buy longer tickets. The basic one day admission to the Disney theme parks is around $71 now ($60 for children). That gets you into one of Disney's four parks for the day. If you want to visit more than one of Disney's parks that day, it will be about $119 ($108). The more days you visit, the less each additional day costs, up to 10 days. The 10 day ticket is only $230 -- ten times the admission for less than three times the cost.
All those tickets expire 14 days after you first use them, though. If you want, you can purchase an admission ticket which is "good forever". That almost doubles the price, though, for the 10 day ticket. However, it is less expensive than buying that $71 first day again.
I think the best way we can help you is if you tell us when you're visiting, what attractions you want to visit, how many different trips to Central Florida you plan to make over the next few years, and the number and ages of those in your party. Then we can make specific recommendations.