Thereatpost.com is a good source to stay on top of the latest news and threats. There is new stuff posted several times per week, so staying on top of it takes at least a couple of hours per week.
You can get pretty darn good security at a very reasonable cost, but I can't fit much useful info in a Slashdot post. I read a 586 page book just on securing Apache - there's a ton of information to know and concepts to understand. For a business, especially a web-based business, it probably makes the most sense to hire in the right professional to spend a few hours with you, going over your processes and systems. I've been doing web security for 17 years; before that I did physical security and I'm still learning, so there's just a lot to know.
Maybe the most important principle is to get rid of what isn't needed. Turn off unneeded services on computers, don't store credit card numbers if you don't absolutely have to, don't have multiple copies of sensitive data on different systems. I can't hack what isn't there.
If you consult with a professional, be prepared to alter some of your processes to alternatives that are approximately just as easy to use, but different. Sftp is as easy to use as ftp, so don't let "we've always done it this way" be an excuse to not improve your processes. A FEW changes may be much less convenient, but necessary. That is to say, your professional may say once or twice "yes, this way is more time consuming, but it really is necessary for security ". Be prepared for that, but also expect your professional to work with you to find ways to make security relatively painless most of the time. It'll likely follow strict, but painless, rules if done properly.
Security is mostly about process, not products, and much of the best security software is open source, so the right professional won't be selling you stuff, just spending some time to find what you need and get it set up for you, then help your IT understand a bit and know where to find documentation.
The right professional will also be able to explain the purpose of any recommendations in a way that you can fully understand. "Because security " is not a valid answer and is most frequently used by people who don't understand the "security" measures they are improperly applying, often in a way that weakens your system rather than strengthens it. It might seem strange to emphasize this, but I've seen a LOT of sysadmins severely damage system security by trying to strengthen it but not really understanding what they're doing. In almost all cases, the people doing crap "security" couldn't explain in detail why they did what they did, and became annoyed when asked to explain in detail. It's a good way to distinguish the few who know their stuff from the vast majority, who don't actually know what they're doing.