Travel (Ho Chi Minh City)

Hello, I'm seeking advice and resources to plan a trip to Vietnam for possibly a few weeks or months. Could anyone tell me roughly how much money I would have to invest and maybe the best spot(s) to visit. Would I need to speak the language or are there many expats residing there that I could link up with? I'm from Boston, MA USA and I'm really interested in learning more about the Vietnamese people, culture, and cuisine. Thank you! :)