Honestly I got mine simply by search a single letter (chosen randomly) in the user search. Looking for someone with a rank over 15 (helps ensure they're likely to be active on the site) and then just did a Buddy Request. I hit 50 in like 2 days. I probably sent way more than 50 requests but a lot of people (myself included) just accept/add any request they get, it doesn't really do a whole lot so why not? Plus if they don't have the nifty fifty or dirty dozen web badges it's helping them too.
This was how I did it lol. Just requested the people who ranked up and had icons since I knew they used the site, checked back the next day and had my 50. I still request and accept requests from people who have posted in the threads here, but that was a quick way to gather the needed numbers.