How many other people are writing about the exact same thing on the internet as you? Just using lots of keywords isn't going to give you a leg up when there are tons of other people out there doing the same thing.
To get Google's attention, you need the main text of your Hub to be highly-useful and unique to readers. You have to offer something they want and need, and which they don't get somewhere else.
Also, having a whole series of titles that are extremely similar to each other makes them less helpful to readers and doesn't differentiate their content to either them or the search engines.