With this plugin you can set you gamemode easily!
Commands:
/gmc - Sets gamemode to Creative
/gma - Sets gamemode to Adventure
/gms - Sets gamemode to Survival
/gmss - Sets gamemode to Spactator
Permissions:
gmc.set - /gmc
gma.set - /gma
gms.set - /gms
gmss.set - /gmss
Images:
http://imgur.com/a/jtnO2