Always raise 2x blind value if no one has called. No more, and no less. They seem to call on 1x blind value raise, and treat 3x or higher exactly the same. Your goal here is to lose as little money as possible if they call. Fortunately though, I would say they didn't call about 80% of the hands.
If they call your raise, fold immediately after the flop if you fail to catch anything (unless you have an open ended straight or a flush possibility. By flush possibility, I mean you only need 1 more of that suit). I say fold immediately because the AI will always raise, and your goal is to see more hands, and not chance trying to run them out.
Now, if they call before you can raise, just call. Calling when they're not the blind means that they'll call whatever you raise most likely, and once again, your goal is to lose as little money as possible.