My youngest two (twins) are graduating now. One today from Stevens and the other next week from the Air Force Academy. Their older sister graduated from Dartmouth in 2016. I saved heavily for them since I knew that being a business owner I was screwed because that big asset would weigh heavily when college time came. I think I started with the 529's around 2003 and had a pretty good amount saved but it would not have been enough without my one getting in the Academy. The money you put in is post taxes but any growth it makes while in the 529 is tax exempt as long as the money is used for approved college expenses.
We were in Franklin NJ funds but there were probably other better choices. I went with what my financial service provider offered. If I remember right you can invest in any state's funds and use them towards any college. You can even switch the funds from one child to another (Air Force was free so that money went to Stevens Institute which ironically was more expensive than Dartmouth). Certain states had lower expenses and special deals for in state tuition - Nj was not one of them.
Good luck with the college savings, it will be worth it in the long run.