Do you know what she likes? I think a lot of “cool” ideas are presented here, however, remember she is still 6, and kids that age learn a lot through unstructured play.

Toys that have multiple ways to play with them, such as craft beading kits and doll houses are stimulating to the brain in more ways, and often preferred by children to circuit building kits, for example. The latter is well within your price range, if she is crafty.