I have found a niche which is of demand but low in competition. So, I want to build content into it for those keywords I want to rank. I have some ideas of its keywords but that's not it I have to generate more keyword ideas. How can I do it and build content according to it?
Just find out the general FAQ's of that niche and start building content according to it. You said that the niche has low competition right?!
So, if you provide some good links to those keywords then you can easily rank in the SERP's without any problem.
Try to know what people want and what are their basic discussions topics in that niche and build content according to it. For this you can go to forum communities, sites like Yahoo answers and social media groups etc.