Mr Ernest Giles, Leader
Mr William Tietkens, Officer, Second in command
Jess Young, Officer
Alec Ross, son of explorer John Ross
Peter Nicholls, Cook
Saleh Mahomed, Camel Driver
All of these people were on the expedition except Taj who is a fictitious character. He tells his own story but also tells the story of the expedition as well.
I gleaned what the characters may have been like from the journals of Ernest Giles: