what can i do to promote my site fast without investing a lot of time .....

I think You Submit your Site in paid Directory and other your site related website with link exchange this is the best way

 

If you invest money or what ever you have to wait atleast 3 to 4 months to get your site yo get better rankings in the search engines.
be patient and go for the natural methods to bring your website in the good position in google,yahoo and msn.don't go for paid directory submission or link exchange.its better to work manually.
if you site is a product based site and you want your business to grow more instantly then go for the google adwords which is organic method.these are paid ads which displays right side of the search results.if you are rich means you can invest money and you will get more business.