The only thing that I know is patience and grinding.
Level steps are about 5.000 at L67, and they grow to 10.000 until L80, 58.000 at L90 etc, exponentially. I had 250.000 between L98 and L99, and I've not yet arrived...
The continuous day played bonus brings 880 max, which is more than any single game. Try to keep it running, grind on and be patient.
It helps to seek some fun here!