Will this have much effect?

I plan to give my site a boost in traffic. It currently gets about 500 uniques a month.

If I pay for directory submission to 500 sites, social bookmark to 200 sites will this result in a lot more direct traffic, or is it only good for backlinks?

If this is a waste of time, what is a better way to get targetted traffic?

The better way would be to pay for targeted traffic, well,
that is what I would do.

Getting traffic directly from directory and social bookmarking
submission doesn't really work well in my experience.

For seo, maybe you need to research they keywords that you can
rank well before doing backlinking.

No point going after keyword that is highly competitive but
you just don't have the skill and knowledge to compete in it.

Nonetheless, if you enjoy what you are doing, nothing would be
a waste of time

The directories will be OK as low value links. SB - probably no value.

For traffic, use Twitter. Join a retweet club and put up good lists of [whatever] e.g. Top 10 Wordpress plugins for the Thesis theme, then you will get a lot of RTs, leading to traffic. This works for a real site, e.g. a blog, but probably not if you have an MFA or affiliate site.

Is traffic from twitter any good?

What about paying for blog reviews?

You will not get a lot of traffic from link dirs for sure.
About social sites, you could get it only if you submit some really interesting story and have network of 50 or so diggers or propeller friends to bust your story.
Forget other social sites.