I think intelligence is something that comes naturally through life experience. As kidsis says; something you enjoy and find interesting will make you content.
I have been studying psychology for three years at degree level and despite the fact I’ve got good grades it’s my knowledge of history, art and politics that my parents say make me stand out and therefore intelligent! I’m changing me degree path at the moment I’m changing to a degree where I choose my own modules which I’ve looked through and it will be in those areas. With psychology it’s interesting but I’m tired of it at the moment, I found biological psychology fascinating it gave me a bio view of metal illness and information on schizophrenia I didn’t know!
I feel I haven’t necessarily been educated with the books I’ve read but I’m not alone in thinking this, sure I know things but it was a bit self explanatory but then again psychology is a new field really, it’s very young.
I think you should search for what you find interesting and go with that and through that you will be educated, books aren’t a waste of time they’re full with so much so just because of the psychology for dummies book (well done on reading it but it’s not a very good book as I have it and have flipped through it but rarely use it) what interests you? What does your mind wonder to (not mental illness way) when you’re pondering, history, study of those around you (which can be sociology as well as psychology), how things work etc there’s so many venues for education go with what interests you and through that you will find knowledge and experience which makes you intelligent.
But remember intelligence isn’t everything so many great minds didn’t go through the typical education systems and many failed when they tried to. It doesn’t take intelligence to make a wonderful, beautiful mind!
Take care, go steady,