I will be in the minority on this, but.
Learning jquery is a great tool to have in your pocket. When I first started with the javascript API, knowing our systems and development group uses jquery, I started to learn and try to force all things ESRI over to jquery.
I spent a few months awhile ago stripping all the jQuery out of my code. I found that I can natively do everything I want, usually better, with DOJO. Plus the library is already loaded and I know it works with the js api because it is tested with it.
So preaching aside, if you have to use jquery then absolutely do it. If you are trying to learn a framework just for working with the javascript api, you will be much better served, both in ease of use and in gained understanding of the workings of the api itself, by learning dojo.