The typical budget of 99% of the folks on DP- nothing! lol Seriously, minimal budget. Maybe a grand. maybe. :O)
How about buying 1,000 .info domains and a dozen hosts with different C Block IPs and interlink them all. Then fill them each with 1,000 robo garbled pages and put a link to your site on them. This expirement would cost about $ Several Thousand if bought the info's for lowest I can find at domainsite.com for 2.99 each. Really though I think Google is smart enough to figure it out at some point that its a trick.
Become a free hosting or free blogs site... which of course lets you put advertising and links around all the sites created on your servers. You might have "quality issues" though... Offer a banner rotation service, with the requirement that the code used to display the banners gives a link to your banner service. Come up with an amazing idea, or perhaps know the founders of some large site personally, so they can seed a wave of buzz, and launch a really cool and important idea that takes over in a storm of posts, comments and links. You don't have to do something totally unique that nobody has done before, you just have to offer something that has real benefits for people, so they'll take advantage of it and want to tell people about it or that imbeds a link for you when they do use it.
It can be done if you have a social networking site. One site netvouz has over 4 million backlinks. That occured from social bookmarking plugins that their site is included on.
thats easy I think its achievable flood other sites with your ads and spams send lots of messages and emails