You might also want to look at balancing what items each purchase gives you. For example, the basic fruit one gives you bananas, but I couldn't do anything with them for quite a while. I didn't know when I would actually be using them so I ended up collecting 100s of them. If there was a way of seeing how they were going to be used, it might have given me an objetive to work towards. This could be done, for example, by showing all recipes from the start, but only revealing the ingredients you have so far. A recipe that was say 'banana, ice and sprinkles' would show up as 'Banana, ice and ???' until you get sprinkles for the first time.
Idk if that made sense, but thats maybe how I'd do it.