Search and content needn't always be different.
Sit down and think first.
Say, camera is your product. Let's assume cost is primarily driving camera sales.
Your search keyword may be "cheap camera NY". You can get away with it, if nobody else who has a cheaper camera than yours is bidding on that keyword.
But when you are advertising on content network, if your product is not that cheap, your ad of $199 will be shown on a site which sells $100 cameras. Not good. So in this case, target sites which provide information, but do not attempt to sell. Or, placement target sites where the product is either more expensive or has lesser quality, so that your product's ad will stand out.
With content, 20-100 keywords per adgroup will do. 20-50 in most cases. Look at the top sites where you want your ads to appear. Look at the keywords they have. Now, design the ad groups based on that. Each ad group should target a specific category of site. If at the end of the process, it is identical to your search adgroups, don't fret.