You have an online electronics business and you’ve set up an ad group for digital cameras. What keywords could make this ad group as effective as possible?

You have an online electronics business and you’ve set up an ad group for digital cameras. What keywords could make this ad group as effective as possible?

Brand names of your top competitors’ cameras
Words from headlines on your website, like “electronics” and “sale on cameras”
General phrases related to photography, like “camera lens” and “camera base”

Words in your ad text, like model names of digital cameras