Whatever genre for which you hope to write, that is on what you should focus.

It is easy to get excited about a new online contest, opportunity, or, chance for exposure—that entices you away from your genre.

Still, you should think about "sticking with your bread and butter," so to speak—your genre—when first starting out. That is your best chance to develop a solid story voice for your work.

If you are just looking to have "fun" with your writing, then, by all means, trying to write a host of different genre stories will give you that.

However, if you are serious about developing a "voice," for a specific genre, then that is on what you should concentrate.

For you to take part in this, that, or the other online "writing opportunities," just because each might be where interest is high, may only bring about writer's block, because of your wavering genre focus.