How long does it take to get a website to a respectable ranking?

This very much depends on competitiveness of your chosen field and strength of sites within it.

It also depends on your own level of personal commitment. If you’re prepared to put hours in, you will get there sooner.

Contrary to popular myth, it’s hard to get good rankings and harder still to make commercial returns.

To be successful you need to design a site that appeals to search engines and humans.

Comparing and contrasting:

Can listings in directories help my rank on Google?

Google leading search engine considers several actors in its ranking algorithm, firstly it considers text content of a sites web pages and decides what theme it belongs to.

Next it looks at number of links inbound to each page, particularly important are links from related themed web pages.

So a web page about domain names, using key phrase domain name registration with lots of links inbound from related sites such as other domain registration will do well.