Long-Tail Keywords – specific keywords usually with 3-7 individual words in a phrase. They are highly targeted and MUCH easier to rank for than broad keywords (all mine are long-tail). The lower your domain authority (check using OSE), the less competitive (more long-tail) your keywords should be. If you can get more specific and the keyword still shows up in Google Autocomplete, Moz Keyword Explorer and other keyword tools… choose the SPECIFIC one.
Always disclose your affiliate relationship. Most visitors will probably understand that graphic ads will lead to your getting paid, but if you write a review or use an in-text link as a recommendation, you want your readers to know that may lead to compensation as well. This ensures you retain transparency and trust with your readers, but also, it's required by the FTC's endorsement rules.