First of all, sign out of skype and skype video. It's linked with messaging and it will drain a lot of the battery. Signing out will really help to increase battery life
Second, on settings>battery> check which apps can run in the background and disable the ones you don't need running in background like whatsapp. Messaging needs to run in background so you should enable that one
Don't keep services on like wifi and bluetooth if you don't need them
If you are doing simple browsing and chatting, use 2G when on cellular instead of 3G or 4G
Make sure automatic updates are disabled a that could download updates while using up battery life when you need it most