What the heck are you trying to write anyhow?  :lol:
Your friend was right. 人 means person. It reads "hito" alone, and usually reads "jin" when in a word. 
If you ARE trying to write "pen person", then ペン人 is ok. Or ペンジン, like you had. 
Just FYI, gaijin (short for gaikokujin) is literally means...