The most common cause of leaking basement walls are gutters/downspouts that are not moving water away from your foundation. Check all of them after a rain to make sure that the water run-off is well away from your house. The second most common cause is the ground next to your house does not slope away from your house, allowing the water to run off...but rather, allows water to run towards your house. These two problems, if they exist, must be fixed first by repairing or replacing gutters/down spouts and/or by regrading the ground next to your house. These two problems probably account for 90% of leaking basement walls.
Paints and sealers, in my experience, offer little assistance in keeping water out of the basement. Hydrostatic pressure (the pressure of the outside water pushing its way inside) will eventually push off any sealer painted to the inside of the basement walls. If your gutters/downspouts and grading are in good order and your basement walls still leak, you will have to have a drainage system installed around the inside perimeter of your basement walls. This will simply allow the water to fall to the drain pipe, and then drain it to a low corner, where a sump pump will pump it out.