The rice crackers I've seen a typically around 2-3g of carbs, so depending how many you eat and how it effects your bg you will only know by trying, peanut butter is about 12g of carbs per 100g so again it depends on quantity, however it is quite high in calories so do keep this in mind.
Daisy1, who welcomes our newbies, will be along soon with some very good basic information for you. Meanwhile, 2 tips:-
1) Read all labels! It's total carbohydrates you are looking for, not just sugars. All carbs turn to glucose in your system.
2) Get yourself a blood glucose monitor and some test strips, and test before and 2 hours after every meal. It's the only way you can find out how different foods affect your blood glucose levels.
Don't be afraid to come on here and ask any questions you like. It's a bit like driving - we were all learners once
Hi PRD I already posted the basic information for newbies which you will find on your introductory thread if you haven't already seen it by now. Good advice from Viv about testing.