You can put a maximum of 1,800 watts on a 15 amp circuit so the number of LED lights that can be put on the 15 amp circuit can be a lot more than you probably would even put on one circuit since LED lights use less watts than an incandescent light bulb.
Typical LED bulbs in houses use from 9 to 12 Watts per bulb.
At 12 watts per led bulb you could put 150 lights on that 15 amp circuit but I doubt you would.