I just bought an iphone 6 from someone and can't activate?

I just bought an iphone 6 from someone and can't activate because my sim is not supported or something. My sim doesn't have a provider anymore and got disconnected. If i take my moms sim and put it in for activation can i activate it and then take it out after. Will i still be able to use the phone without a sim if i activated it already?

Christmas

Probably not

To use the mobile network you need a valid SIM card in the phone.
IPhones us a nano SIM.
If the phone is network locked, blicked or iTunes locked you are in trouble.