I think the key to writing engaging articles is to choose topics that you think are interesting. Along the same lines of MB Hunter above, read other articles, see what you like, and build on the base of knowledge.
I would avoid tryng to write about the spectrum of financial topics, just to round-out an archive. Even the best financial experts have their strengths, and if you start writing about things you don't like or bore you, then it will come through and you will lose readers.
Write what you like to read. I have deleted several drafts that I think are tedious. Better to do this than put your audience through it too.
Hunter.