what's the best way to level up EXE ?

https://preview.redd.it/u8m63sz4p4pe1.png?width=147&format=png&auto=webp&s=b149a585cf1f42b7dd87683b1f6ecdc69043eed9

I currently have him at level 40 and I wanna gold him but I'm really slow at leveling up monsters compared to some of my friends who manage to get gold EXE in like half the time it took me to get it to level 40