With overclocking you can not just be told settings. You yourself have to push up the clock on the core maybe 20-30mhz. Then play a full game of say Battlefield or a game which is demanding. If you don't crash then you can push the core clock up another 30mhz.
Continue doing this until you do crash and back off to the last step.
That would be your maximum overclock on stock voltage.
After that do the same thing for the memory clock.
As for temps, anything below 80 degrees is fine. 80 degrees is the so called safe threshold for this card and most cards. Although it's up to you some people like running their cards at 90 degrees + 😉
Although 80 degrees is the known threshold..