Bento cooking is my passion. I love the boxes and taking my lunch in them. I just learned this style of cooking recently for portion control and the thrill of the cuisine.
The important thing to remember is, you don't need all the flash cooking items, you could go broke buying them. As soon as you can create the passable Sushi and know you will be making the rice often, THEN you get the Zojirushi Rice Cooker. (I also cook my oatmeal in the rice cooker)
Technique and basics. Learn to make Dashi
first, it's the broth you cook your rice in. Start slow and build up. Learn how to make Miso Soup.
You don't need the bamboo mat to make Sushi Rolls, you can use plastic wrap, waxed paper, etc. Get the technique first. And for goodness sake, ask questions.