The goal is to have no standing puddles of water after use. We need to make sure the highest part of the shower floor is always the perimeter. From that point, the floor needs to begin it’s slope to the drain.
So how much slope is needed? Anywhere between 1/4″-1/2″ of slope in 12″ is acceptable. Not enough slope could prevent surrounding water to find it’s way to the drain. Too much slope could be dangerous and more slippery especially when soap and shampoo residue is on the floor.
I always use a Schluter Shower Kit that comes with a factory pre-sloped shower pan that takes the guess work out of the slope and provides an amazing connection with the drain itself. Schluter offers a 10 year against shower pan leaks, best in the business to date.
If you want to add an additional layer of water protection, try using Super Grout Additive at the shower floor and curb area. It solves that dreaded grout cracking at the shower pan perimeter and is 99% waterproof. Use in on the curb corners too, a very common weak area that can allow water to escape the shower door and go outside of the shower onto the floor causing possible water damage related issues.