There are many things in your kitchen that you do not need to spend a lot of money on. However, everyone needs at least one awesome knife. About 2 months into my stint working as a line cook I treated my self to a
Global 7 inch santuku knife.
Out of everything that I have bought completely convinced that I was making an "investment" (heals, jeans, the list goes on...) this one truly is. It cuts beautifully and when I use it, it almost feels like and extension of my hand. It keeps me from cutting myself and allows me to to do everything I want.
For the small lesson: How to chop an onion. Trust me, with a good knife and a solid cutting board (one that doesn't wobble is very important) your will be a pro at this after a few attempts.
Start with an onion fully intact, cut in half horizontally.
Remove outer, undesirable layers (this is much easier once you have halved the onion).
Make lateral cuts across the span of the onion. Don't cut all the way through (top to bottom) leave the top end intact so that the onion holds together (this will help with the next step).
Now cut horizontally, you can vary the width to make as fine or coarse as you would like.
There you are a perfectly chopped onion.
Often one onion is too much for what I am making, if I just want some for a salad. In which case I just put the rest in a a jar with one half red wine vinegar and the other half water. This will leave the fresh and just pickle them a little.