I have played 36 times so far (I checked). I have no idea if there is another level after 15 - it keeps beating me so I don't know if there is a trophy or not.
Pizza Guru - I like that. Ummm my pattern goes
Level 1 - nothing
2 - upgrade shoes
3 - nothing
4 - another topper
5 - another dough maker
6 - nothing
7 - another oven
8 - another topper
9- another dough maker and upgrade one oven
10 - upgrade other oven
11 - upgrade one topper and upgrade shoes
12 - upgrade other two toppers
13 - upgrade all three dough makers
14 - nothing as there is nothing left
15 - I don't know cuz I can't beat it
As soon as the level starts I make dough then go over to the customer and then I memorize (real quick) what the toppings are so I don't have to look at them (as in pepper/meat/mushrooms and sometimes I just give them colours (green brown white) which ever works for my brain at that time) - then I just click on them without thinking. I also get plain pizzas in the oven as the person is ordering (I know this ahead of time) so they are out of the way quickly. I also click on the next dough size I need before I leave the machine this saves a lot of time. Then finally I try and make Berry walk as little as possable. As in I will take out a pizza from the oven then click on the line of people waiting for me to take their order as I am moving down the line to deliver the pizza - instead of going back and forth.
I hope this helps with your strategy
Good Luck