You will probably want a foot model for lower limb, but otherwise your school's resources should be sufficient. I would not recommend purchasing a skeleton.
No, a whole skeleton is completely unnecessary in my opinion. If anything buy a foot and ankle bone model and stop there. Plus it's easier to transport in a backpack, I wouldn't even buy the entire lower extremity like some do.
At DMU for gross anatomy, you and a partner get basically an entire skeleton in a bag. That being said my partner picked it up way back in August and I haven't looked at it since. Bones and their landmarks are the simplest thing to learn, IMO.