Let me do an example and hopefully some can tell me if I'm doing this right!

So I have four cards to a flush after the flop which means I have 9 outs to hit it on either the turn or the river. Now by going by Phil Gordon's book, my implied odds are 36% of hitting it. According the article, my pot odds are 20% (9x2+2) and that means my call has to be less than 1/5 the pot? Or is that wrong?

Now, first question: What the hell is the difference between the two and which should I look at? Do I go by the implied odds and does that mean my bet has to be 1/3 the pot or I have to have 3-1 odds? Why are the pot odds different?

I guess I'm just lost.

I know that with the implied odds, if I have at least 25% I should make the call and considering I would have 36% after the flop, I should do it?

OR do I combine the two to make my decision?

As in, with the implied odds being 36% and justifying the call, my call still has to be less than 1/5 the pot for it to be the RIGHT decision.

Any help??