Don't waste time, gather every effort to build your list first.
1.Ethically post in forums,
2. Video's on Youtube
3. Article publishing
4. ebook giveaways..
build your list folks!
points to ponder,
By doing keyword backlinking you are getting there in top spot, but may takes a lot longer time to compete, (but will be rock solid for at least untill your competitor beats you with more backlinking)
by doing all these above, let say no.1 - Ethically post in forums..you'll get instant laser targeted prospects..
lets do this for at least 5 days, without fail and see the outcome in the # of signups..