So I meet for the first time ever my nephew who lives in a completely different state than I do about a week ago, since Easter is coming up I was thinking of spending him a Easter basket through the mail but would it be right of me to send it to him even though I have not done anything for him in the past? If so would there be anything recommended to put in the Easter basket/

Send it if you are interested in building a relationship, but not if this is a one time deal. At 3 he is likely into cars and trains, and may have a favorite TV show/character. I always find summer things to be great for Easter baskets... swim trunks, beach towels, sidewalk chalk, shovels, pails, bubbles, etc...