The amount of creatine you need depends on several factors, including your diet, sports needs, and the type of creatine you are taking. It's best to stick with the recommended 5g dose of creatine monohydrate per day, although other types of creatine like creatine HCL may only require a 3g dose. Always check the bottle as most creatine supplements should have instructions for both creatine loading and maintenance dosing.
As for when you should take creatine, it's recommended to supplement shortly before or after training. Around 30 minutes maximum before or after exercise seems to be the sweet spot for many athletes.