It was a lot easier when you could actually see the parts, with all the modern surface mount components, now you need a microscope to see a resistor!
When we were about 10, my twin brother and I started with a very simple single transistor sound amplifier. By the time we were 12 we (and our older brother) built a Heathkit color TV, a year later a tube oscilloscope from scratch, and then he went on to make all kinds of
neat stuff, but I got into cars instead.
Maybe one of those old 200 in 1 Electronics Experiment kits like they used to sell at Radio Shack would be a good place to start? They have big enough parts that you can see what's going on, along with good literature explaning how the circuits work. Look on ebay or thrift stores...