It will take forever unless traffic to your site is coming in by
the thousands daily or your visitors are kind enough to click on
them. Because from what I remember, the rate for CPM ads (cost per
thousand impression) is below a dollar, unless your site contains
adult material. If you have quality content, I would actually
suggest buying the CPM ads here (it's fucking cheap at $0.02 SGD,
or $0.03 for sgGirls.com, per CPM, which I'm considering to
purchase as well) to link to your site and place Adsense ads
there.
And by the way, Adsense would probably have earned a lot from
naive webmasters (which I once was) through unpaid payments due to
its minimum $100 policy. So you would want to consider that before
joining the slaves who are doing free labour for them when the
quota is not hit.
You may wish to look at other advertising programs that are much
more well-paid than Adsense (btw, Adsense is not really that good
on the publishers' side) as well. One of them which deserve some
consideration in my opinion is Text-Link-Ads.com. But I guess that
you're planning to place ads on your Blogspot site, which may not
be compatible with their scripts.
Another alternative would be to contact potential advertisers
directly. You'll need to be confident of constant traffic flow to
your site and quality content, of course, and this method gives you
the most bucks versus all other methods since there's no middleman.
Some may even offer a commission for you per sale completed as
well. For example, if you own an established anime blog site, you
can call up small retailers selling anime-related merchandise such
as figurines and DVDs to ask if they are interested to work out an
advertisement deal with you.
One more would be to run your own advertisement program. Kinda
tedious, since you'll need the server resources and advertisers who
are interested to place their ads on your site. One great example
would be sgForums.com itself. But as mentioned earlier, it is
selling its ads at $0.02 CPM, so I don't think you would want to
compete with that.