I am travelling for the first time via Dubai.
Is 1.5 hr layover sufficient for connections of Emirates flights?
If Emirates will let you book it on one ticket then it is sufficient transfer time and if you book it on one ticket and your inbound flight is delayed Emirates is obliged to get you on the next available flight.
Plenty of people manage the 1.5 hour transfer but you will have to move quickly and won't have time to do anything other than follow the transit signs, go through transit security and head for your next gate.
As Latimer says, if you were allowed to book it then Emirates think it's sufficient time. Proceed to your departure gate as soon as you come off the first flight. Terminal 3 is huge so it can take a while to get from one gate to the other. No need to worry but just don't dilly dally.
Ask for help and they will assist and maybe even provide a buggy.
EK arrives and leaves from Terminal 3. Starting with your own TV screen on the arrival flight, information boards, signages, staff meeting the flight, and if you miss all of these, there is Transfer Desk. 90 minutes is fine but you may not be able to take a break for anything.