If you're looking to purchase a gen 3 night vision device (NVD) such as a PVS-7, PVS-14, etc. you need to plan to spend more to get the right accessories and equipment to properly use & enjoy it.
Wearing your NVD
You can start with using the standard head mount (aka skull crusher) which is normally included with -7's & -14's but trust me you'll hate it. The best way to head mount these devices is to wear a plastic "bump" helmet and attach your NVD to it with a mount. Bump helmets are much lighter than ballistic. The popular Ops Core Basejump, Team Wendy Exfil LTP, and SAR Tactical really are the best. There's a reason they're popular and it's because they are well made, conform to the head well, and include a night vision shroud to attach a NVD mount. You can find cheaper air soft replicas but their shrouds are cheap plastic which will break causing your NVD to fall off and hit the ground. Not good. You'd have to buy a proper shroud and at that point you'd be close to the price of a real Ops Core or Team Wendy. There is nylon head gear like the Crye Precision Night Cap that works okay with a single PVS-14. You'll need to buy a shroud as they don't include one. I recommend a helmet because you'll want more stuff like infrared lights, strobes, patches, etc. PVS-14's normally come with a j-arm which has a thumbnail camera screw that goes into the -14 and it has what's called a bayonet horn that plugs into mounts such as the Rhino II. PVS-7's come with the bayonet horn attached to it's housing so it doesn't need a j-arm. The mount has a plate that inserts into the shroud. A lot of new users get confused over arms, mounts, and shrouds. Don't be afraid to ask questions.
Accessories for your NVD
The #1 accessory you'll want is an infrared illuminator. This is basically a flashlight with an infrared LED. I recommend getting a dual spectrum light such as the InForce WML IR or a Surefire V series (Vampire). Dual spectrum means it puts out both visible and infrared light. This is useful because you'll need white light to see stuff with your NVD flipped up and the IR light helps your NVD see better when it's really dark or looking into dark spaces where moon or starlight can't go. The #2 accessory is a lanyard that attaches your NVD to your helmet. This can be as simple as DIY paracord. Wilcox offers retractable lanyards that can attach to certain shrouds or webbing ran through a bump helmet. PVS-7's and -14's also come with sacrificial lenses that cover the NVD's lens to protect it from getting scratched. I personally don't use them unless for some reason I'd be wearing my NVD's in a dust storm in which case I'd put them on.
The #3 accessory I strongly recommend is a signaling device that attaches to your helmet or body. If you'll be out with other people using NVD's get a dual spectrum strobe. You want dual spectrum for your friends with NVD's will see it in IR mode and if you're alone to activate the visible mode for people without NVD's to see it. A visible mode is crucial if something happens to you and you call for help. A bright flashing visible light will do the trick. You can use a handheld visible flashlight but if you become unconscious or incapacitated you could drop it or release the activation button. The strobe will stay on and is attached to you. A good alternative is a headlamp that has a flashing SOS or beacon setting. Also, the battery run time is much, much lower with a flashlight turned on versus intermittent flashing. I also recommend a strobe or steady marker to stick on your dog if you'll take him along. I prefer visible mode on my dog if I'll be anywhere near other people because I don't want someone mistaking him for a coyote and taking a shot at him potentially hitting him or me.
There's a ton of night vision related gear but for beginners I recommend starting with these 3.