You can pretty well skip both if you want or don't have time.

With Agents of S.H.I.E.L.D., the movies affect it more than it affects anything in the MCU. The show has gotten a lot better since the beginning, but it is still a network series. It's usually really good, sometimes a little silly, but I personally love it.

Agent Carter is pretty cool, but because her story takes place in the past, you don't necessarily have to watch it. I did lose interest in this one though as the seasons progressed. I don't think I watched either season finale.

Agents of SHIELD gets really good after Captain America: Winter Soldier.