Running paid traffic to affiliate offers is where a lot of beginners lose money fast. The mistakes are usually pretty consistent. No tracking set up before spending – If you can't see which ad/keyword/placement actually converts, you're flying blind and burning budget. Scaling too fast – Doubling a budget on a campaign that's only had a handful of conversions is gambling, not optimizing. Ignoring the offer's terms – Some programs explicitly ban certain traffic sources or bidding on brand terms; getting banned after spending is a brutal way to learn this. Not testing multiple offers – Putting all traffic behind one offer means one underperforming page can sink an entire campaign. Judging results too early – Killing a campaign after a few hours of data instead of letting it reach statistical significance. What's the costliest paid traffic lesson you've learned?