Remove the sunflower seeds from the mix and add pumpkin seeds. Give the sunflower seeds as treats. To improve it further you will have to do some searching.
I bet he's glad to be with you, it usually takes ones I get a few days to adjust to chomping cardboard. With 11 adult gerbils we get through loads and can never have enough, I even bring it back from the shops!! I have all my friends and family collecting for me!!
Just to add to the cuteness factor of the post here are the baby gerbils my mother got me 4 weeks ago (this was taken 4 weeks ago). She got them from a free to good home ad, because I had after a lengthy battle lost a black and white gerbil. I thought they were male and female when they arrived but they are both male. I wasn't best pleased with my mother at the time because I had enough on my plate with 3 rescues that came the same day but I have forgiven her as these boys are so cute and funny.
Coffee
http://homepage.ntlworld.com/yunfey....s/Coffee01.JPG
Scamp (aka MimPea)
http://homepage.ntlworld.com/yunfey....ls/Scamp01.JPG