I will use the tool to pull in a lot of keywords related to a theme and group them into relevant topics. These topics will either become their own content page or will be combined with other topics to create a page. KeywordTool.io is similar to other tools out there such as Uber Suggest, which I've used for a long time, but it tends to produce more keywords and it provides search volume for the keywords.
2) SpyFu: I suggest to have paid account on SpyFu. I just need to find my competitors who using Adwords and review them using this tool. It will show me what ads and keywords they are using. Note that my competitor who paid for that particular keyword knows exactly that it is important for his business including recent trends. Also using SEO feature you can input any URL and find our which keywords they are ranking for.
It would be great if you can provide comparative analysis of this tool with Google Keyword Planner. Since you’re using this tool so you can provide best comparison. One differentiation which I understood is that this tool works for yahoo and bing as well whereas Google keyword planner works only for Google but Google being a dominating search engine, gives the highest returns, so only this reason may not be enough to buy it.