The research wasn't very hard. I bought some straps and installed them to get the hang of it. Its actually very easy, and now they make quick release straps, so you can change out your strap every day if you want. Mostly it's a fashion blog, so the companies do the work for me by putting out great photography.
I've been doing it about a year and a half. The first 6 months I hardly made money and almost gave up, but then I wrote a popular article and managed to rank quickly and and people purchase watches through it.
I don't really do keyword research. Most of my money comes from two or three articles, one of which is about a particular watch. So I could write more articles about other watches when I have the time. But I have a full-time job that I love, so I only do this for fun. I've done some advertising on Pinterest that seems to have been useful, and Pinterest itself brings in visitors.
I used to write a lot of content but got a new position at my full time job that's been taking up a ton of time. When things settle down I'll write more. Other people hire writers, I'm not sure about that just yet. I don't do reviews, mainly because I didn't want to handle the shipping of bands back and forth. Seems weird to keep the review bands, although plenty of companies have offered free bands I've never accepted any.
I'm an Amazon affiliate, and also Etsy & Jomashop (a popular online watch seller) and one or two others that I've never got a sale from. I usually don't get compensated from featuring independent strapmakers, unless someone buys through Etsy. But they provide the interviews and a lot of great photography, so I basically feature them for free. The blog would be boring otherwise and they're very talented artists and fun to work with. Check out Combat Straps (https://www.combat-straps.com/GALLERY.html) or Jones in Tokyo (https://www.etsy.com/shop/JonesInTokyoLeather) and you'll see what I mean.
I'm not interested in my own straps or watches, there are enough people doing that already so I'll stick with my quiet little niche. My website is just a WordPress theme.
Hope that helps. Check out the reddit link for r/juststart. It really is very informative and fun. This is my second business. The first one was an iPad travel magazine that failed miserably and never made a profit, but was also a lot of fun.