Hi,
Generally to improve the loading and the speed of a website , we use a cache plugin ( w3 total cache), we use too " wp Smush it" to improve the sige of images, we use wp dbmanager to manage the request to data base, and also we use webmaster tools to correct all the errors, we set the permalink correctly, so wwe give interest to think to the structer of our permalinks , and we adjust the plugins by using P3 ( plugin performance profiles) to see which of the plugins ask a lot the datbase, and which the best plugins combination to give you best sped , and at the end check on gtmetrix.com
cheers,