Traveling and electronics are not at the top. Anything involving money services is where the money is at. I know plenty of people with little to no tech skills making 6 figures a year with Adsense. The key is to make a site that gets visitors looking for something in particular. Your site should be about that subject. Your title and description should be written in such a way that they think they can get what they are looking for. Your site should provide just enough information to get you ranked for the terms you want and get ads targeted to what your visitors are looking for. The site should also be good enough to not lose your ranking by a hand penalty. If you are in a good money making sector your competitors will make a spam report about your site guaranteed. Your content should not provide any solution that will send them on their way without clicking on an ad. Your goal is to get them to click on the ad. Don't say anything to that affect of course because that is against the rules.