It may be the camera/lens. What settings are you using and kit do you have? I would stick with a more entry level first and get to grips with that. Its a bit like the bedroom DJ getting an all singing and dancing set of decks before he can even mix. A 5d is also very expensive and you probably wont use any of the features. :p
I can get half decent photos with my 1,100d (not a great DSLRT) and f3.5 kit lens without a flash. Have to be on at least 2,500 ISO and a shutter speed of 1/80th. The withe 70d and any one of my 2.8 lenses are fine without flash, but it takes a much better photo with a fill light. Every single one of the photographers I recommend use flash and most also off camera flash too for FD/evening. Increasing the light and decreasing settings drastically improves the photo. I was shooting at 800 ISO & 1/250 shutter last night. I had a horrible Yongnuo flash so it could have done with a diffuser to soften the light (bit harsh). Its not a great photo, but this is good enough for Facebook etc. Shows everyone having fun. :)
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