So long as a domain is 12-18+ months old, link development really isn't a problem - though better to grow a campaign if possible.
As for gaining links - my strategy so far has been centred on building sites for link development purposes, but these days I also use two private brokers as well, to help get the most with themed links.
So, in other words, the best way to get decent links in the first place is to control the sources.
If not, use a mixture of varying link sources and quality. Enough quantity works with lower quality.
Also, for directories I'd go for quality not quanity, and not make it your main strategy.