ASoon I will need to make a small crib with gum paste. Can I glue it together with candy melts, or do I need to use royal icing? I have never made or used royal icing. I was wondering if candy melts might be easier.

Candy melts should work.  I prefer using tylose glue.  Mix 1/4 tsp. tylose and 2T warm water.  It won't look right at first but it will completely dissolve by the following day.  Another option is egg whites, just warn people if they're wanting to eat it, though I don't recommend eating gumpaste anyway.