What combination of Competition, Average Searches, Average Clicks and CTR (Click Through Rate) is ideal?

There is no ideal combination that will work for all listings. Generally, we recommend that you use multi-word tags and highly relevant phrases that people are likely to search for (e.g., long-tail keywords). Keyword Explorer and the Keyword Tool can help give you some good ideas on where to start. Having lower competition can make it easier for your listing to appear on page one, and keywords with low or medium search volume are often long-tail keywords that may be used by potential buyers when they are closer to purchasing.