Interest can also be something that fires your imagination. In the stories section you can see that one of the things that fired Einstein's imagination was a simple compass. Magnets can really make you think if you take the time to give thinking a try. What questions do you have about magnets for instance?
I would like to pursue my interest but what should I do?
You can find some advice here. But don’t stop here, ask for more help if you need it. But if you really want to have fun making things for hardly any cost and lots of fun and learning, try here.
There are some ideas and links here which you might want to consider.
Electronics, Cooking, Computer programming, Gardening, Astronomy, Microscopy, Maths - yes this can be one of the most interesting things of all if you give it a chance, Chess, Engines, Psychology, Geography, History (well almost any topic really - yes anything you want) - it just depends on what you are interested in.
What makes a good interest (thing to do) which will help you learn?
Answer - anything.