I'm assuming you are a beginner, in which hitting 300+ great! As for hitting higher, that comes in with time and patience, but most importantly, if you want to hit high, use monsters with abilities such as Magic/Force III and Adaptability.
Once you have those, upgraded and stat betted well, you can hit at least 1000 minimum, with the exception of physic since ghost type is considerably underpowered.
In my opinion, ghost and water are easiest since as ghost you have the deadly Felicity, and with my other monsters such as Rhor and Neon, I hit up to 1200. With water, its even better, Patta, Rhor, Neon and Felicity, I can hit up to 1600! so hitting up to 50000 per day isn't that hard on water day.
Pretty much, you just need to focus on your main team first, then once you have at least one gold and the rest silver, you can get other monsters just for world boss. And get Force III/Adaptability.
Hope it helps!
