For bedrooms generally you will need to dig down to footers and properly waterproof and French drain the walls on the outside. You can add a dimpled membrane to the inside of the walls, cut the slab around perimeter, add a drain and sump system and replace the slab. This method isn't nearly as good as the other and typically doesn't save much. It's used in unique situations where you can dig the outside- say in a city with zero setback to the sidewalk.
Proper surface drainage (as suggested above) is also a high priority. But a leak is a leak and you need to fix it. Doing a basement remodel without would be like putting a new paint job on a car with a bad motor. It may look pretty but it ain't gunna work right until you fix what's hidden.