Sig campaigns are overrated, people mostly want them as a source of income and post count boosting. Don't believe the hype 
That's what I initially thought, it may just be a form to make some small income on the side for some people...
If that's hype, then what's the best way do you think Altcoin4life?
Well you could limit your sig campaign to hero members and above for example, i dont think twitter or facebook advertising is that good unless you make an audit of each account since most of them have bots, fake people, etc. so they would be pretty much advertising your site to no one.
Good giveaways is more than enough in this section or games and rounds to start promoting your site