Note that, it is a fact that some of the more popular Blog Niches' are so saturated (in terms of competition) that it may take years for a new blog to gain recognition and craft a place for itself in the given niche.
However, if you are not willing to wait so long and want to see quick results in terms of higher rankings and reputation (and the resulting gains) in a given niche, its important that you choose a Niche for your next blogging project where the competition is less intense.
Possible content ideas for the 'pet and pet care niche' niche
Here are a few content ideas for your 'gardening' blog.
D. Ancient civilizations and their way of living.