You need to concentrate on targeting your "lowest hanging fruit" as I like to call it.
The way to do this is by properly finding out 3 crutial things:
1. Find your target market, who are they, what do they spend a lot of time on.
2.Find out what it is the need to hear in your tweets that make them ingage.
3. Present your product/offer in a way that resonated positively with their needs, wants and desires.
If anyone needs help with this feel free to add me on Skype: ericsebastion