Everyone dreams about owning a luxury watch, and that industry is never going out of style. You could start a blog about Luxury Watches and target a developed country such as the US. Make it a platform for reviewing, discussing, and possibly trading luxury timepieces. Alongside the blog, you could run a classified ads section for buying/selling luxury watches. The popularity of luxury watches remains constant, with potential end users as well as vintage collectors.
Your articles can be on each luxury watch brand, model, and reviews on the same. Enrich the blogs with information as to where to buy, sell, or even get the watches repaired. You may want to target smaller regions in the US first if you intend to provide information in physical stores and repair shops. This can be a very satisfying blog for watchmakers and watch-lovers alike.
Blog Name Idea: LuxuryWatchesUs.com