Treats are a great way to tame your birds but I wouldn't use it to train your birds for trapping. Your birds should trap to your feed call. Some people use spanish peanuts, safflower seeds, and some even use cheese crackers. I use the peanuts personally. Feed them the treats in your hand so they get to know you more intimately and when you earn their trust you can pick them up without any problems. This comes in handy when you start road training and you have to pack them up in the release basket.
I get my peannuts from a couple of different places.
you can get them from the grocery store if you like but they tend to be a bit more expensive there
make sure you get unsalted unroasted peanuts
some pet stores will also sell peanuts
I personally like going to ann's house of nuts
they have every kind of peanut you can think of there