I think that, as your first site, an all-encompassing review site will leave you overwhelmed and underpaid. Considering you're new, trying to compete with other giants (AND niche-specific sites) for review traffic is going to be incredibly difficult.
However, if you start breaking down your niche, then you can do laser-targeted reviews and be competitive for those certain products within your niche.
Right now you want to do something like this (random examples):
Review site -> reviews the Xbox One, 2 types of whey protein powder, and the newest Macbook
You should try to narrow it down to something like this:
Whey protein powder review site -> Reviewing each individual brand based on price point, effectiveness, user reviews, etc.
The whey protein example was just an idea - that niche is ridiculously competitive, but you get the point. As your first site, you want to hone in on a small niche and try to dominate it.
You can use google.com/sktool to estimate monthly search volume, but don't let a low CPC throw you off. Unless you are monetizing via Adsense, you have a plethora of other options to try out - for example, let's say whey protein powders had a low CPC (it doesn't)... you could become an affiliate at some major health companies and sell through that, earning a commission on every sale instead of every click.
Also, keep in mind that you will be competing with *fake* review sites run by marketers who know more about SEO than you. You have to bring something new to the table!
In this post I did not cover even 10% of what goes into internet marketing as a whole. It's a complicated beast that's difficult to master (or even keep the motivation to earn your first dollar.) Good luck!
Jared