What and how many guns should I have during M4

I’m having trouble deciding what guns I should be going after for my crit build. I differently going to get all the legendary Jackob I can but I’m trying to figure out any other good guns with elements since the M4 and 3 have modifiers that could make my normal bullets do less damage. A problem I always think I have is that I have too many guns in my inventory since I want room for any legendary I find while killing. So how many guns do you usually carry with you and what types are they?