Can you test an app before you buy it on the iPad? I want to buy an app, but don't want to waste money on something that's not gonna work for me.  Is there any way to test drive one?
Sometimes app developers will release a version that allows you to play with it, but to get full functionality you need an in-app purchase.  See this app for Summoner Wars as an example:  https://itunes.apple.com/us/app/summoner-wars/id493752948?mt=8

But this is a choice the developer makes, so if the app you're interested in doesn't supply something like this (or a lite version; see @Alex's answer), then no.