This is especially easy to do in any of the battle challenges, such as Auldnoir Time Attack or Endestria Time Attack. Auldnoir and Pleajeune Time Attacks have less enemies at a time, so you may find it hard to find enemies, however there are no airborne or ranged enemies early on. Endestria Time Attack has heaps of enemies and is almost entirely airborne, but given most of the enemies are ranged, you can get hit easily if you're not careful, which will force you to start from 0 again. Start one of the battle challenges, then immediately fly into the air. Start Gravity Kicking the enemies, making sure that you never touch the ground or get hit by enemies. You are allowed to fly around between Gravity Kicks, you just cannot touch the ground or get hit. You can easily get 10 before your energy runs out, though it will be significantly easier if your Gravity Kick and/or your Gauge Usage are at a higher level.