I think it varies so much it is hard to say.
Some women I know have 3 baby showers and literally need nothing.
If you are taking the basics, you need a place for baby to sleep, a carseat, some clothes, diapers, wipes, diaper rash cream, receiving blankets, and bottles if baby will be ff. You can start out with just a few hundred dollars.
However, ftms especially think they need lots of stuff right away. Like target is in another country. They want finished nurseries, complete with matching bedding, decor, and glider. They buy an expensive stroller right away, bouncer, swing, video monitor, hooded towels, baby bathtub, fancy pacifiers with cases and wipes, wipe warmers, etc. You can drop over 1k in a baby store without even thinking.
I know because I did it. We spent a fortune on our first. I thought we needed these things, and half weren't used for quite a while. I recommend buying the basics, waiting until baby is here, and getting what you need.
I.e. I still love our wipe warmer. I admit it.
There is an awesome book out there called Baby Bargains. It has a pretty decent budget in there for various expence ranges.