Buying links on those kinds of sites for SEO purposes is a waste of time. The link has almost no value because there are so many other links on that page and Google could ban that site (not your site) one day for selling links for SEO reasons.
The Google terms now state that you should use the no follow tag in a link which you have sold, rendering it useless for SEO.
The only time I would say yes to buying such a link would be if it actually generated traffic which converted. For that website I don't think it would.
As for Adwords if you do it wrong it can drain your finances extremely fast, however if you do it right it can be the best adverting resource in your media mix. When one of my clients first came to me they were only using Adwords and turning over £264,000/year. After a bit of tweaking of their Adwords account and landing page their turn over shot up to just over £1 million for the exact same spend. Need I say more?
To Kanchan: There is plenty to know about SEO. Start reading forums like this one and if you really want to get into it you might want to consider buying an SEO course. The SEO landscape is always changing though, so the SEO learning curve is never ending.