What type of sari would best suit me?

I'm 16 years old, 153 cm tall, rather plump with dark complexion (not very dark either). I have to wear a sari for a function at school. I need it to make me look taller and slimmer and it shouldn't be too casual or too dressy. What kind of fabric and color can the sari and blouse be? And is there any specific style I can try out ?