For a 24 foot pool, you're good to go with 1 gallon of 5.25% bleach (no name walmart brand for about $1.00). If you're questionable on the water source and feel the water should be brought to shock level immediately then add 3 bottles.
For your size pool, get 1 container (approximately) 2 lbs of CYA - that's cyanuric acid, also known as stabilizer or conditioner. Place about 2/3rd into a sock and tie to the stairs, don't leave it near the liner, it's relatively corrosive.
Measure your CYA level using the kit described above after it has dissolved (about 2 days) and add more if needed. Keep CYA level between 35-50ppm, do not add too much since this is something you can only deplete by removing and replacing water, and too much of it makes your chlorine less effective forcing you to run higher chlorine levels.
For everything else, read the post under the appropriate chemical sections of teh forum, it will show you how to apply the BBB method of pool maintenance, the best method hands down.