Having certain items on a device and not the other

I'm fairly new to apple products. I have an iPhone 4s but Ive almost used up all my memory on it. To resolve this issue I am getting an iPod in order to store some of the apps,pictures and music from my phone.

Anyway, if I use the same Apple ID on both devices can I still delete items off one device and keep them on the other device? And can I download certain things on one device without them appearing on the other device? If so how do I do it?