What they say is not true. They're only telling you half of it, google are renowned for not telling you exactly how to do your campaigns properly cos all they are interested in is taking your money!
The display url
has to "land" on the same top level domain.
i.e
domain1.com = display urltracking.com = redirect url or affiliate url (destination url)
domain1.com = landing page.the above is ok.
if it's like this.
domain1.com = display urltracking.com = redirect url or affiliate url (destination url)
some-other-domain.com = landing page.then you can't do that.
I thought we had this discussion before, I mentioned that I tried that program before and their landing page didn't convert very well. So I did my own and it converted much better. Plus I was bidding on keywords where the asking price was 50 cents or below, I ended up paying like 4 - 12 cents per click.
You're better off promoting your own website with their product. Far more control.
If $100 a day is too much, then you need to work out what you can afford.

it works with any amount.
Start with say $20.00 a day MAX limit.
Double the CPC google asks for. (but do your keyword research first).
Then next day reduce the CPC to the price google asks..
then the next day deduct 10-20% off the top price.
then the next day, take 5-10 cents off the bid until you're not in position 1 any more. Once you're not in position 1, put the price back to where it was previously.
Important: always make sure that your campaign name is related to the keywords.
ie.
Weight Loss = campaign name.
lose weight = ad group.
keywords.
dieting tips
lose weight fast
etc,
no more than 7, or fewer to increase overall CTR percentage.
Ensure that you only do broad match here. with negative keywords like
free
cheap
simple
easy
etc.
then create another campaign, similar names to above, this time do exact match... repeat above.
then do another campaign, but do this for phrase match.
and only target one country at a time in any one campaign.
and turn off content network.
create new campaign for content networks. select sites for site targeting campaigns.
search for dieting forums, websites that have adsense on them and add their urls to the site targeting lists.
It will take a while for you to get this right, it's no easy task. I lost like $6k in my first attempt and gave it a rest for a while. but with practice, you'll get a hang of it.