When you have a sump pump, you need to rely on the water getting to the sump before it rises to a pressure higher than the floor at any place you care to protect.
If your basement floor is on gravel, you can get by with a sump pump at a convenient place. If the sub-base is not porous you might not get the water to the drain before it comes up through the cracks at places far from the drain.
The one thing you absolutely can't do is seal the floor to prevent water from entering. The slightest water pressure will come up through cracks, and water with a pressure that makes it rise more than 3" above the floor will usually break the floor.
A round sump is best. You can cut back the earth under the edge of a round hole and line it with concrete bricks without mortar. The circular liner will resist collapse. Put a layer of small stone in the botton so water can get through to the pump.