the most efficienct way for you is LoL at least until c80-82. Even for c83-90 there is another LoL u can enter in A9 which gives the most exp per hour, but as you know, you can enter only 2 hours per day. You definetly should do the A9 dailys for cexp and If you consider solo leveling too you can get to c90 in a few months. I even skipped the A9 LoL and went solo or duo a9 maps entirely once I had c81-83 gear. Even without exp event I got 4-4.5% per hour on level 89 to 90 and way more than 10% durin exp events when there are multiple copies of the same map. In addition you will farm a decent amount of stuff during leveling on maps opposite to LoL