The best niche for a newbie is a niche that you truly understand, having knowledge of it, and passionate about. Base on your blog topic then you will decide which platform will be best to drive traffic to your blog. Let's say you're passionate about home gardening, then for sure Pinterest and Google will be a great traffic source for your niche.
Always validate where is your audience available online, you can use Google trend & Google Keyword Planner, Pinterest audience insight, and Facebook audience insight to get the demand data for your niche.