The niche is important but don't stress yourself about it
Think about some things that you are passionate about
Then think and see if you would be able to give people advice on that subject. It can really be anything
After you find something, do some research on google and see what kind of products or services you would be able to recommend to your readers on that subject (niche)
For ex. if you're passionate about weight loss and fitness that can be your niche and with something like that you would be able to promote weight loss pills, Gym memberships, exercise equipment or even paid exercise videos. (T-25 or anything of that sort)
Mostly just be patient and you can always re-adjust your niche and approach to your blogging
Best wishes to you,
DJ

Stay excited... that will carry you much further than being nervous ever will.

Bounce the ideas off people and get feedback here in WA.

Ultimately good with your passion, something you can talk about forever. You'll be just fine, keep learning and stay excited.