I ordered what I thought was a good basic set and sent it right back (had to pay a return fee). It had mostly tiny pieces and not enough bigger ones to be useful. The price ($53.77) was also ridiculous. That experience taught me to read reviews and check other place for prices before ordering any Lego sets. The $29.99 price I paid for this set is the right price for this selection of Legos, not the $50 or so amount many sellers are charging.
This set (#10662) has a good selection of basic bricks in a variety of sizes.
This is the ultimate Lego starter kit. It has all the basic pieces you could need. Some of the pieces are silly, like the build-your-own Lego person and the rotating square "steering wheel," but I think they just give kids more options on how to build. This kit is better for making buildings, or as the directions suggest, animals. It only has one pair of axles and wheels, so this is not great if your builder wants space ships or a fleet of army tanks. One down-side is that some of the tiny bricks already have cracks in them after only two months of use, but I don't think they will end up breaking and the bricks still work fine. This is true for the other Lego sets we own as well.
So glad to find a source of assorted Lego blocks to provide stimulation for creativity rather than building something according to the printed plans and pictures. I plan to buy more assortments for my grandsons.