The material you are going to buy should have a warranty that will specifically state what your leveling requirements are. Make sure you know. If the warranty doesn't say, ask the supplier. He should know.
Without knowing how thick your "new wood floor" is, or whether it is composite, laminate, raw t&g, or prefinished t&g, there is no way for me to answer your question. I can say that it needs to be pretty level, because you will feel it if it isn't when you walk around, and the floor will be begging for squeaks if you have to bend the flooring at all to go over humps or through valleys.
An out of level floor can indicate structural issues that you might want to take a look at. Foundation cracks, settling, shifting structural members, etc.