All in I have about $1700+/- in two AEGs and a pistol. One AEG has minimal internal upgrades, extensive external upgrades. The other... Well, lets just say the only thing stock from my M4 is the actual gear box casing itself, upper and lower receiver, and the outer barrel. Everything else has been swapped out for Lonex parts (gears, inner barrel, motor, etc) and many external Magpul goodness has been added on. Pistol has a minimal upgrades as well.
In total I have probably dropped about $6k+ into everything from gear, accessories, upgrades, and guns. This has all been done over the past year or so. It was a gradual process. One impulse buy, but that ended up getting sold.
Bottom line is over the year I have spent a majority of the money on upgrading my AEGs and changing through gear. I do milsims on a regular basis and as such, each big event I seem to find a kink in something with regards to my gear that I want to fine tune for ergonomics and performance. Same goes for my AEGs. I'm at a point now where everything I currently own is fine tuned perfectly, so my next step will be a project GBBR. I still have another set of rigs to buy in a different color now that I have fine tuned exactly how I want my rigs set up for my tan loadout, and know my preferred play style, but this just means buying all of the same carriers, belts, etc in a different color.
This means that over the next year I will probably dump about $3k into a second loadout and my rifle project, and this will be over an extended period of time. I have learned that the best thing is to do it in steps. Take the most important steps first, and then slowly add on after as to not burn a hole in your wallet.
Now that you have four guns, it's time to get the gear to support your toys, and by the time you finally have all the gear to support them and have gamed them a bunch of times, you will start noticing things you want to fine tune in the gear already purchased, as well as your weapon platforms. It's a black hole for money; the biggest thing is to remember not to go on a spending frenzy with your credit card because you've "just gotta have it now". That my friend is a dark path, and prevents you from adding on to your loadout down the road, unless of course you don't mind being a couple grand in the hole.
Take your time, do the research before buying ANYTHING, as very little in this lovely sport/hobby comes cheap. When it comes to actual gear, invest in quality stuff, especially when it comes to PPE. Your eyes, teeth, face, and anywhere else on your body you deem pretty and/or valuable are not worth damaging to save yourself $50 here or there. You also want gear that makes sense and works for the role you intend to play as. If you don't know what I mean, there are plenty of threads on this site and videos on YouTube displaying various load-outs and gear set-ups specific to certain play styles and weapon platforms. Check them out, do some personal research (beating the dead horse), and then proceed from there.
Guardians of Asgaard
NO EGO, ONLY HARD WORK
Primary - Z-Custom VFC ZTW
Secondary - KWA ATP