Many guys into milsim like to use as much real steel as possible.  But since prices are sometimes prohibitive, here are some of my picks for some alternatives to real steel.  I have personally used each one of these and found them to work just fine in "normal" use.  Meaning I don't jump or dive them; I don't try and abuse them.  Just general patrolling/milsim, and even some live fire use.  

SOTAC "W" style 5/8" riser and flip mount: around 80 bucks.  This is a great riser and flip mount combo for a RDS and 3x mag, for use with NV.  Flip mount uses NV-style shoe, which makes it easy to use mag as hand-held mono for scanning.

SOTAC "W" style G24 mounts: around 75 bucks.  I have used these with both mono (-14's) and binos (BNVD's).  They held up just fine.  In fact, with replacement nylon-tipped screws, are actually tighter than originals.

SOTAC "K" style RQE: around 150 bucks.  This is considered one of the best, if not the best, dual device dovetail mounts out there.  Extremely hard to find original.  East to find replacement, which works quite well.  

SOTAC "K" style OSS: around 75 bucks.  This allows you to mount -14 on right eye, with RQE.  

SOTAC "K" style "K" clips: around 45 bucks.  This allows you to mount a thermal with "MUM" style mount to left eye, with RQE.

Somo Gear PEQ-15: around 260 bucks.  Perfectly usable LAM.

Sky-Tac Comtac III: around 150 bucks.  Perfectly usable headset.

Sky-Tac V2 PTT: around 70 bucks.  Connects headset to radio, in this case a UV-5R with Kenwood 2-pin.

Baofeng UV5R: around 25 bucks.  Perfectly serviceable comms.

TRI "I" style M3 bone mic/earphone: around 75 bucks.  Nice for when you don't want full ear muffs.  

Holy Warrior "E" style RDS: around 125 bucks.  Decent RDS for the money.  

Holy Warrior "E" style 3x mag: around 120 bucks.  Decent 3x mag for the bucks.

HAO "G" style 1.93" 30mm mount: around 150 bucks.  Nice high mount for LPVO with NV.

HAO "G" style Mk 16 rails: around 80 to 100 bucks.  Actually very nice rails; very comparable to real steel.  

I post this here FWIW.  These are all items for milsim use, which work perfectly well for training.  Since many of the real steel items are higher priced, some ridiculously so, these might make a good budget alternative for you.

If you still want real steel, you can find them in the other forums.

I will add some of the non real tac stuff I have used over the years:
Bump helmet: I have a TW I got used (I know I know f them)
I also have a PTS mtek flux replica helmet that's pretty decent.

I use a CADEX mount for my PVS-14 (I got it used for $50)

I have a messed up back, left knee and right shoulder so I use chest rigs instead of plate carrier (plus chest rig is just much cooler in hot weather) and a condor battle belt set up with H Harness.

Some guys go for exact real tactical stuff: I don't I've ruined several real steel/tactical things such as:
Point Blank plate carrier (ripped to shit at Copperhead a few years ago)
Salamon boots (didn't last a weekend constant walking in water at a Veterans for Airsoft game at Black Ops in Wisconsin)
Ops Core Bump helmet (rachet system broke after 5 years of use at game in Indiana, replaced and broke again after used 2x)
Oakley gloves - ripped at two fingers after 2 milsim west games.
Crye pants caught and ripped at abandoned asylum game on a piece of rebar.
There is probably a lot more I just can't think of.

Also I've heard the Argus NV Mount is pretty decent for the $ I might pick one of them up also for $150.

I've had to wear ballistic plates and helmets for hours on hours my bodies already paid a price for it so I don't have anything to prove to anyone, you want to wear it that's cool by me but some of us older guys are kinda done with impressing anyone. But: I am looking at doing some impersonations like: Son Tay Raider, Marine Raiders or Army Rangers from WW2.

Oh Yeah, I did get an Argus mount awhile back.  Good piece of kit, for the money.  Also replaced screws with nylon-tipped ones.  Tightens the "barrel" right up.  I don't even use my Wilcox G24 anymore; it's the older model with no lightening features or extended reach.    

Got a bunch of stuff on order as well.  Will update as it gets in in and used.

Any updates on the knockoff rqe/kvc stuff? Had the real bridge backordered for over 3 years (oss and k clips came in last year) so I'm looking to try the knockoffs. Do you need to replace the screws in the knockoffs?

No sir, 3 YEARS for IOP order. Hence my exploring the Chinese knockoff that has initial decent reviews.

No, Knights Armament hasn't charged me till they're ready to ship the items. I was a bit annoyed that they increased the prices of the items a year or 2 into the backorder. Nothing to really be done about that though. UNLESS the china knockoff turns out to be a suitable replacement. If that happens, I'll consider cancelling with Knights. I ordered the knockoff this afternoon. We'll see how it works out