In my opinion, many if not all were original to him.  Influenced by things he’d heard and (possibly) read, but not copied.  Storytellers are all (without exception) affected by earlier storytellers, but the best of them still tell stories that express their own ideas and sensibilities, and thus create something sui generis, that has never existed before in that form. 

There is no convincing evidence Jesus was particularly influenced by any religion other than Judaism.  He might have had some exposure to Samaritan beliefs, but Samaritans were basically practicing a more archaic version of Judaism, that more modern Jews felt was barbaric. 

In college, I took a class on Oriental Philosophy, and our professor, who was from the Philippines, used to say there was a ‘Daemonism’ that led to similar religious ideas cropping up independently, all over the world, without there necessarily being any cross-pollination required. 

Although Gautama Buddha lived roughly five centuries before Jesus, the religion he and others inspired was not well known or understood in the Roman world.  Even highly educated pagan Romans knew little about it, though there are scattered surviving writings that indicate some awareness of its existence.  They tended to see Buddha as yet another god one might worship if one wished.  Not quite right, but what the hell. 

Interestingly, there is some evidence that Christianity influenced some much later Buddhist stories, which may have helped create the misconception that Christianity borrowed from Buddhism (there is a Buddhist virgin birth story, but no reason to think that was something the first Buddhists believed). 

Buddhism, like all religions, constantly changed throughout the centuries, and the earliest Buddhist texts we have were written down centuries after the death of Gautama Buddha.  The gospels, by contrast, only a few decades after Jesus was crucified.  Makes a big difference to scholars.