I want to improve my concrete basement floor, but not too much
Get a contractor to take a look at it for sure. But I suggest to you that you will really need to rip out all the old concrete, re-prep the substrate and level it before putting in any new concrete. This will be the only good way to get a decent long lasting floor. Make sure to include heavy gauge wire mesh (5x5 or 6x6 inch grid) and re-bar if called for. When the slab is the proper thickness (3.5 to 4.5 inches) this can really help keep it together in the case cracks develop.

While you have it all opened up you should strongly consider adding drain lines along the bottom of the foundation over to a sump in one corner to help divert water from coming in on your new floor.

The type of patch up fix you asked about is really a waste of money because it is unlikely to last. Especially if you intend to use it for a shop floor.