There are two sides to this... traffic and your conversion rate. They really ought to be two separate discussions.
Here's a thread which looks at getting more traffic:
How to get more than 500 visitors/day?
On conversion rates...
One good way to increase your conversion rate is to create an in-depth case study of a product or service, describing in precise detail exactly how it has helped you.
If you enthusiastically recommend a product which solves someone's problem, you're halfway there.
Also, you need to think about how people are finding your site and what they're looking for.
Ideally, you want people who are desperate for the answer to a problem to be discovering your site AND your site needs to recommend a product or service that solves the problem.
For example, if you write about "Firefox plugins" and they find your site by typing that phrase into a search engine and then they find free, helpful information, that's very good for building your reputation. That's good for the long-term view, but isn't likely to generate much revenue today.
1. Have a prominent sentence urging people to subscribe to your RSS feed to get more good tips.
2. Ask them to subscribe to your newsletter to get a useful free report. A newsletter gives you multiple opportunities to make sales. A newsletter also helps you win readers' trust.
3. Do some video reviews of your favorite products. Post them to YouTube and then take the code YouTube supplies and paste that into your site. Videos are powerful.
No. You're not expecting too much. $100 a month is a very modest goal. In my Affiliate Program Tutorial I recommend newcomers should start by aiming for $300 a month.