Hey guys, I've done limited research on NVGs and am on a slight budget. I'm seeing there are parts kits available, minus of course the image intensifiers. My questions are;
Is there any money to be saved after assembling your own?
Is it best just to buy complete from a reputable company?
Either way, I've seen mention of ways to purge tubes after disassembly, has anyone purged their own?

Thanks in advance, and my apologies if this has already been covered, I'm slowly reading through the other threads in this forum.

Well, this is a contentious issue.  You will get many opinions here.  First of all, I understand you are on a tight budget.  OK from that perspective, yes, you can "roll your own" -14 and save a significant amount of money.  Now, that being said, it is not an easy task.  The actual assembly is fairly easy, although many find ways of fucking it up.  So I guess I should say if you have good mechanical skills you can pull this off, but that's not the difficult part.  The reason why this task is hard for a beginner is because most guys lack the knowledge/experience in examining/choosing which parts to buy.

So for the newbie, on a budget, the best option is to link up with a SME who can guide you through a buying experience, of a fully assembled, used unit.  These can be found for anywhere from 1200 to 2000 bucks.  This is probably the least amount you will pay for a good gen III unit.  If your mission is simply to obtain good gen III NV, this is the way to go.  

The next level would be to build it yourself, which again I would recommend doing under the direct supervision of a good SME.  If you also would like the experience of building your own, besides just acquiring NV, it will probably cost a bit more, since you are hand selecting parts, which means unless you just find a bunch of smoking deals you will probably pay a little more.  Complete kits, minus tube are around 685-1000 bucks.  Tubes are anywhere from 1,000 to 3000 bucks.  So here, if you buy a new re-build kit, and a good used tube, you could come in around 1700-2000 bucks.  So really, you gain nothing going this route, unless you just want the experience.  Purging the tube can be done at a home workshop level.  You may need help from a weld/fab shop with the gas, but it's doable.

The next choice would be buying commercial, with an outfit like NGI, which assembles really good Gen II tubes into -14 kits.  So you get a really good gen II tube, just under the gen III spec, for about the same price as a used gen III, or building gen III.  

The next choice would be buying new gen III.  This is the end state you are striving for, getting good gen III NV, with the least amount of risk.  But also the most cost.  Here you are looking at about 3,000 for good light filmed green phosphor.  Yes this is expensive, and probably beyond what you want to spend, but I include it because it's really the best choice for a newbie, with no one to guide him, to get good NV without getting hosed.

So I guess it boils down to your access to the knowledge and experience to obtain this stuff, at a discount.  It can be done, but the path is fraught with peril.  Unless you have someone local to walk you through it, you are taking big risks in the process.

If you score a good deal on a tube, it can be worth it. I bought a gen 3 omni 7 tube with a damaged pig tail for 600, and a parts kit on ebay for 650. For under 1300 I have a PVS14 with a great image that needs a slight smack once in awhile to turn on. 

Much appreciated guys, I assemble electro mechanical components at work so I'm fairly confident I could assemble one. I suppose similar to an ar parts kit, as uninvolved a process that is, it would be a good experience to be able to work on/build my own setup. The parts kit I'm looking at is $650 and currently I'm searching tubes.

It would appear an auto-gated tube is the safest bet though, longevity wise. Maybe I'm understanding it wrong, but the auto-gate helps prevent damaging the tube?

You can build a Omni VII high spec tube PVS-14 for $2,200 with zero blems having mid range mechanical skills. The things to be aware of is there are 2 sides to the retaining ring, work in a dust free environment, keep cleaning/using canned air to blow off the dust, keep your canned air vertical, pay attention to which way the pig tail connects to the housing, read up on how to adjust your infinity stop on the objective lens, make sure your tube lock ring is good and snug, and use a silicone based electrical grease on your o-rings. Purging is simple by using dust off type canned dry air. Slowly spay into the purge hole above the on/off switch expelling the air inside of the unit with canned dry air. Reinstall the purge plug and your done.

*****Now the reason people buy form a reputable dealer like JRH, TNVC etc is: warranty support 5-10 years, high select tube spec (at no extra charge) when you buy from them you know it's done right and if you FUBAR the tube install you just now spent way more than 3,000 for a professionally built unit.*****

Yes. When bright light is seen by the tube, it'll turn on/off the tube very rapidly to avoid burning a spot onto your tube. Think of it as ABS on your car. Nice to have when you slam on your brakes, but it doesn't mean you want to drive like an idiot and use it all the time to avoid an accident.

Best deal out there is a warranty. Hard to save enough to justify giving up a ten year warranty.  I've built my own twice and had good luck, but I bought new guaranteed tubes. My first PVS-14 was bought used as an assembled unit and was a POS. I didn't know what to ask, and what to expect. I ended up with a very dark unit full of blemishes. Pretty much useless without an illuminator. So I bought a new tube and replaced the old tube in my first rebuild. At least I salvaged the price of the unit without the tube and the accessories. So I now have a high spec WP filmless PVS-14 that is the shit! I have almost $4800 into it, but I built it and the tube is warrantied.