I advise that you pick one, perhaps two of the niches you mentioned, and stick with what you chose. If you really want to write about them all, then you can either spread it out over multiple websites (the worse option) or wait until/if your site grows large enough for you to diversify (the better option). Splitting your focus is no way to succeed at anything, especially something as cutthroat as the world of online content.
Next (after you’ve picked your niche), you should ask yourself, “Am I going to write all this, or am I going to buy/outsource?” There’s nothing really wrong with either of those options, but the more professional the content, the greater the chance of your site getting traction.
You said that making your content interesting is your chief objective? Well, then your course of action will come down to answering one question: do you consider yourself a good writer? If the answer is yes and if you think that you can regularly produce content in the niche you’ve picked, then I see no reason for you not to start working on your site (and its content) right now.
If not, then you will certainly want to hire a professional content writer, preferably from a reputable service. They will take care of all your content-related needs.