My honest opinion is I think its better to work on one good blog first. When it gets traffic and starts making money then you can make more sites. Doing too many at once can make every blog grow slow. this is mine one you may disagree thanks
If this is the frst time you are working on something like this, I would advice you to start off with just one blog, which will make it easier for u to establish topical authority and to find out how things work before moving forward with another niche website.
Either option could work I think but if u r starting from scratch I would concentrate on one website first. Managing multiple sites is time consuming and it is easy to let quality slide when your focus is split. A solid, well mainttained site is a good foundatiion to start with before u think about diversification.