The examiner wants to see that you can operate the aeroplane safely and make sensible decisions. The examiner will act as a passenger so know what you have to brief him on. You can expect to have to calculate the take off distance and determine if the weight and balance is in the envelope; if you have not done this before your training is lacking. How much fuel will you need for the flight (including reserves - he may ask you what you are including in your reserves). You will get a number of aural questions so know where things are on the aircraft and what they do. e.g. What are you looking for on your final Mag check and Why?
Your instructor should advise you if you are suitably prepared however it seems he has missed out some fairly basic training:
I've never actually done any flight performance stuff before
I've never had to use the track error methods during my training