It's definitely hard to say for sure.... I went back and forth on getting a pump before the baby came just in case I had some sort of issues which prevented me from bfing. But then I went to epinions.com and found a good deal on the Medela PIS Advanced and decided to go for it. I brought it to the hospital and the LC there saw it and offered to show me how to use it. I was really grateful for that. Although it's not difficult, I know the last thing I would have wanted to do after having a baby is read directions for a new piece of eqipment! I also think having the pump motivated me to stick with bfing since they aren't cheap and I didn't want to feel that I wasted my $$!
It turned out that I had a lot of problems initially with my dd's latch. I had a terrible crack on one nipple which then became infected with yeast. While trying to heal it, I pumped on that side so that my dd would make it worse. I also had an overactive letdown so it made it very difficult for my dd to latch properly - my milk would literally come shooting out to fast for my baby! So, on the advice of my LC, I pumped for about 2 minutes before bfing, just to relieve the pressure of my letdown.
For me, having the pump before the baby was a lifesaver. However, a lot of women have no need for a pump in the beginning. When my friend had her baby, the LC told her that she didn't need a pump because the baby was her pump.

You can always buy a pump after the baby arrives but depending on how fast you need it, you may or may not have time to look around for the best deal (if that makes a difference with your df

) Another option is to rent a pump from the hospital if you really need it but that can be a bit pricey - I think it was around $50/ month at my hospital. Maybe you can research now and wait until after your baby is here to actually make the purchase. With the exception of having the LC show me how to use the pump, I don't think I really used the pump for about 2 weeks when my problems started showing up.
And definitely save that Lansinoh until after the baby is here. I had a small tube, though, and only used about half of it even though I used it all the time.