I would use pine shavings more so than straw because it absorbs better. when it gets really dirty that's a sign its time to change it out. some people(depending on your climate) use sand and say it works great. For me the pie shavings don't work well in the nesting boxes, but I never found anything that works amazingly for it.
Hope this helps and I hope you have a good time with your chickens!
Also, welcome to byc!!!