おかげさまで would be an appropriate answer for in-laws, clients, business partners, friends/acquaintances who give you support etc.

For おかげさまで, it would be when you are humble about something, which means "All thanks to you", depending on the tone, it can mean sarcasm or really "all thanks to you". For 元気です, its when people ask you お元気ですか？"How are you?" as a greeting, and you reply 元気です "I'm fine"