And I would like to build a simple robot that is controlled by RF; a robot that is not a kit.
you do realize you will have to make your own RF transciever, right? its hard stuff to design on your own, although many schematics can be found online to copy . . .
Are kits good for learning or are the kits just a matter of construction?
a little of both . . . depends on the quality of the kit. many kits hide all the technical stuff from the builder . . . but more that is hidden is less the builder learns . . . when you select a kit, select one that you think you will learn the most from
And maybe some good kits that would help too.
search this forum for robot kit