What animations do I need for a character and a weapon?

I’m a total noob at animation and I want to know where to begin. I’ve got a model for my character already it’s rigged and such, I have a weapon I also will rig. What I want to do is have the character be able to hold the weapon, as well as different weapons, and also each weapon have unique reload animations involving the weapon magazines. Would I have to make a different character for each weapon and animate them together or can I animate it seperate somehow and link them together perfectly. How would I ensure the animations line up, and in total what animations are needed to make a character, like do I do the legs movement seperate from the upper body etc