We read the books and stuff, and they helped some, but real work experience trumps everything. First boy was a tough sleeper and inexperienced parents made that more difficult, second was super easy, third was in the middle. Kids are like evil AI robots that learn and adjust, so the second you think you've got them figured out they'll test you a different way and turn things upside down. So I would suggest having a clear expectation on what kind of a parent you see yourself as and try to model that. We have so many parents who spend SOOO much money on their kids and cars and stuff and get them whatever they want. We said we want our kids to be good people, disciplined, know how to work hard, we don't want to spoil them, make them thankful for what they have and how tough it is for so many others, etc. I think I would try to model what kind of a parent you want to be and what kind of a child you want to raise and then work backwards from there. We have some friends who want to be the "fun parents"... I've seen that story play out when I was young and I certainly don't want to be those parents.
For costs, depends if you are going to be nursing or supplementing, buying or making food. Diapers cost a lot and will be a big expense, but food is fairly minimal early on. Think if you want to start saving for college in a 529 plan or something and then what daycare costs will be, as that is the biggest expense we've ever had and those years were tough. Are you going to have 1 kid or multiple, as cars become an issue. DW upgraded from a Corolla to a CRV to a Mini-Van (I tried to get her to go from Corolla right to Mini-Van but was shot down). I kept my 2003 Corolla and found a way to get 3 kids in car seats across the back (it was hard, but doable). I love the mini-van though as you'll have so much crap for kids.
I would also try to get as much second hand stuff as you need. Kids treat clothes terrible, so we have great neighbors who have older boys and grandchildren, so we get boxes of clothes every few months which is a HUGE saver, including bikes and shoes and boy scout stuff, that is incredible! Find those friends and neighbors and don't be shy about taking 2nd hand stuff or going to to the thrift store for stuff, as clothes can cost very little or cost a ton...
When we started having kids it's tough financially, I don't think anybody is ever ready financially for kids, but we tightened up as much as possible or car/vacation/clothes/food/entertainment, etc. and basically found that we needed to be MMMers to afford kids, so when expenses got less, salary went up, we found ourselves in a much better position financially.
Good luck!