If it is just about brand awareness (which simply means more people know about your brand), that would make an impression the most important factor, the more people find out about your brand the better it is, they can later on purchase, but the purpose of brand awareness is to just let them know about your existence, my analysis would be to make sure that I get more than at least 10,000 impressions per day on relevant keywords, with a good click, CTR can bit low no worries (our main goal again is to let them know), so I can evaluate it to be successful.