What are those risks?
Drawing the attention of lots of entities that you don't want attention from.
Just as GM stated, plus they could potentially hack into your computer, steal your files, id your location, control your computer remotely, you could potentially access websites that have criminal activities - thus drawing the attention of alphabet soup type organizations (NSA, CIA, FBI, USSS, ATF, DEA, NCIS and INS), or even if none of that happened, the fact that you have to use a TOR browser (which can also access "http:www" sites), your local internet service provider (even using a VPN with TOR), they'll know you're accessing onion sites BECAUSE of where their exit traffic is going - Note the following: "A user is talking to a clear net website instead of the onion so in theory the proxy can read all the information you're sending and getting from the onion. Also, you are far from anonymous because the Tor2Web-gateway sees your IP."
https://chloe.re/2016/05/20/killing-tor2web-once-and-for-all/ And (note the web address in the photo here). You WILL get attention from someone. There's no avoiding that. There are also a couple of things I didn't provide above to disguise where you are or who you are, but the bottom line, is if someone wants to find you, they will. A quick query of TOR security precautions will make it so that most people won't find you, but the government and good hackers will if they want to.
I've used the deep web on and off for about two years. Then again, I work where I work and do what I do, so I'm not overly concerned about having uninvited guests. For the most part, I've seen a lot of bit coin operated sites that offer whatever service you can think of, blueprints, how to's, and seedier things. The bit coin sites all work off of an escrow service that can be used to locate someone as well.
GM is correct in saying that it has its risks. I'll add, for what I've seen on it, it isn't worth the hassle, other than just to go cruising downtown Tijuana to go see things that no one else sees for the "been there, done that trip."
Edit: I forgot to add, that if you do decide to access it, disable java. If anyone reading his doesn't know how to disable java, they shouldn't go. Period.
Edit II: Do not use TOR with windows to access the web. As I stated above, the best way is a dedicated machine, using Linux and TOR on a thumb drive into that.
It really isn't worth the hassle. Those curious, can go youtube query "deeb web sites" and get an idea that way without risking themselves.