I'd rather have your kit lenses and a good flash than try to shoot everything available light, even with a fast lens like the 50mm. 50mm on a 1.6x crop body is a short telephoto anyway, not really a general purpose lens like the kit wide.
Bouncing flash is the way to go. I pretty much use my flash in one of two ways:
1. Bounced off of a wall or wall/ceiling combo. I do this when I can get the subject close enough to a light colored surface I can bounce the light off of. Don't be afraid to use walls, side lighting can be very nice. This gives me a nice, defused light because of the huge area the flash is bouncing off of, and can be accomplished simply with just a single bounce/swivel flash unit.
When I use this method I make sure no light is going directly from the flash to the subject, just the soft bounced light. You will need a fairly powerful flash to light up a room this way, and a lot depends on weather you are trying to light up a room to f2.8 @ ISO 1000 vs f8 @ iso 100.
This is a single flash bounced up and over my left shoulder as I shoot. It's reflecting off a mostly white wall and ceiling. It allows me to shoot handheld and move around, adjusting the flash angle as I go. I'm shooting at f5.6 @ ISO 400 in a fairly dark room, but the light is soft, wraps around the young lady and doesn't leave any hard shadows. The fluorescent room lights are turned off (horrid green color) and it's only lit by various Christmas lights. I'm shooting at 1/60th so I can get some of the Christmas lights to glow more. When the room lighting is on, I shoot at 1/250th so I am a few stops above the ambient to not pick up a green cast in the subjects hair, but then I loose the Christmas lights.
2. If I'm inside, but the wall and ceiling bounce isn't an option, I go back to basically direct flash, but with an omni-bounce style defuser over the flash head. This simulates a bare bulb and sends lights in all directions. I use the flash tilted up at about a 45 degree angle this way. This is basically direct flash, which can be harsh, but some light may bounce back from walls/ceilings to help fill in. Having the flash tilted up gets it that much higher and helps reduce red-eye, too.
I only shoot this way if I can't do a real, full bounce. I will combine it with a second slaved flash to get a more pleasant effect if I can. I might also drag my shutter speed to try and pick up as much of the available light (depending on the color temperature) as I can to help fill in the otherwise harsh flash. If I don't have an omni-bounce to put over my flash head I sometimes use a bounce card to direct a portion of the light forward too. This will simulate two lights, the one bouncing off the ceiling and the one coming directly off the bounce card straight at the subject.
TL;DR: Use the Flash, Luke!