3 or 4 clicks per 100 views does not seem to bad at all, at least to me. Vagur has already explained about the CTR (Click Through Rate) for this.
Next is, you cannot compare others as long as your website content is not in the same niche as others. That matters a lot.
Don't add too much of ads to your website to make it more prominent. It will lower your CTR and hence other factors of your revenue
If I understand the exact motive of the question correctly, which is basically to maximize the revenue, then go for CPM based ads which yield you revenue just for displaying ads on your website. There are so many good CPM networks out there.
I hope it helps you.
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