"Obtained" means something came into your possession, usually through your own effort. "I obtained a small stone by reaching down and picking it up." The word "received" cannot be correctly used in this sentence. "Received" means something came into your possession specifically because someone gave it to you. "I received a message on my phone." The word "obtained" is wrong here. You can use obtain instead of receive if you don't want to reveal how you came to possess something, or if the fact that something was given to you is irrelevant to the conversation. "I obtained the money needed to buy that expensive item." The listener may not care how you obtained it. "Get" can mean either "obtain" or "receive": "I got (received) a gift from my friend." "I got (obtained) a new pair of shoes." You can use "got" in all of my example sentences without issue. However, some people, though I disagree myself, view "get" used in this way as informal and inappropriate for formal writing.