I recently bought an Iphone 5c. It didn't have a SIM card (bought it off of craigslist) Itunes won't let me activate it either

I recently bought an Iphone 5c. It didn't have a SIM card (bought it off of craigslist) Itunes won't let me activate it either - 1

You NEED a SIM card. There's no way to get around that.

Now the problem is that you have to buy a SIM card from the carrier that the phone is locked to. If it is unlocked, then you can use pretty much any physically compatible card.

It's is probably stolen.
It is certainly still registered to another account.
It may be network locked or even blocked.