If you publish through a publication, the earnings will be all yours. You won't have to share them with a pub.

As to whether you should self-publish or not, there are different opinions on that. My opinion is that as a beginner with no followers you should definitely go with pubs as they already have an audience. Once you have some followers of your own, you can reevaluate.

As to which publications to send your stuff to, my advice is to experiment. Some pubs will like your stuff and others won't (and that's true regardless of the quality of your writing).