Add more suggestions in iOS predictive when typing
Most keyboards only show three suggestions as you type, no matter how relevant they are to the current conversation. Quick Type, the suggestions in iOS 9, have gotten much better at providing good suggestions that are context-specific, but it can't compare to some third-party options.

Your best alternative would be to install a good, intelligent third-party keyboard for better, more relevant suggestions as you type. I would suggest the SwiftKey keyboard as your best option for both keyboard and emoji support. Another good alternative is Swype.