Watch the Chorus Before OD online guitar lesson by Jeff McErlain from Guitar Effects Survival Guide
Some of the fun of effects pedals is experimenting where you can put them in the chain. Modulation pedals are fun because they can sound very different depending on if they are placed before or after the gain stage. Generally speaking more subtle effects are achieved with the chorus before the OD pedal, more extreme after the OD. Don't let anyone (including me)dictate what is the right order for these pedals. It is what sounds right to your ear.