lol.js

// removed "limit" from query params
var url = "http://api.tumblr.com/v2/blog/manarecs.tumblr.com/posts?api_key=2Waj1PmWwaIcu49hUVPTb4WOwWNOp1uOkhP4vjn0Fe3g7zB7Ss";
$.getJSON(url, function(results){
  // The latest post is last
  var latest = results.reponse.posts.reverse()[0];
  
  // Make DOM element with this latest post data
  // Not familiar enough with jQuery + page HTML to do this
  
});