What kind of tie out chain to get for a dog new to being outside?

I have a Pit Bull Border Collie mix. She's 56 pounds. What kind of tie out to get? What kind of collar to put on her since she slips out of her color when I take her outside to pee now? Is it better to wait till spring to put her outside instead of right now close to winter? She isn't potty trained if your wondering why I'm having to put her outside. My mom said this is the only way. Thanks
 
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