I will also go ahead and say that you will not be happy with a JG, Echo 1, or any other "entry brand". These guns are just that for the most part. they are entry guns designed to be cheap to get someone in the sport, and from my expeirences (I have been playing for 5 years) they will break after 6-8 months. And they will break HARD. You can spend a little more, and get a G&G, KWA, G&P, VFC and expect it to last much longer, and have a better rate of fire. JG and Echo 1 coax kids in by caliming to have guns shooting 420 FPS right out of the box. Mostly this is true, however, most indoor fields dont allow FPSs above 350, and FPS is not everything in airsoft anyway. Aside from all of that, A gun shooting that hard with cheap china parts is bound to break. Its just going to happen.
Again, if you get a KWA, you really shouldnt have to make any updgrades to it to perform extremely well out of the box. All you would really need to upgrade in it is a mosfet to help save the wiring, and then you could run an 11.1 lipo with hardly any problems.
KWAs vary in price, and you can usually find one with a rail system that you like already on it. Much like breaking a gun apart internally, externals do not always come off in the same manner as their real steel counterparts. You cant just Swap out uppers on the fly like you can on a real AR, some models of guns, it requieres a little bit of tinkering to get parts to come off.
Mags, are usually more expensive than real AR mags. If you get highcaps at least. Highcaps run anywhere from 17 for the cheap ones to 35 for good ones and are prone to rattaling and breaking, and a lot of players prefer midcaps (Personally, I like high caps, but that is just me). Midcaps are a little cheapers, ranging between 5 per mag for the cheap ones to 20 per mag for the good ones).
Other externals (Scopes, Stocks, pistol grips, etc) are usually relatively cheap, but also cannot be interchanged with their real steel counterparts (Exceptions include forgrips, bipods, tac lights). I recommend not using a real Eotech or aimpoint for airsoft, as they have been known to shatter when hit with bbs in CQB. Vice Versa, I do not recommend putting lesser quality optics and lasers on real ARs and expecting them to maintian zero, because they wont.
As far as gear goes, the predominanty gear on the market is made by condor. Condor is relatively cheap becuase it is made in China. For about 120 dollars you can have a plate carrier, mag pouches, and hydro pouch. Being cheap has its disadvantages though. With tough use, Condor gear will eventually fall apart. This may take a few months, it could take a few years. Condor products for me have been very hit and miss, and I swore off China Gear long ago.
That being said, gear wise, for about 240 you can get a Quality, American made setup. MAde by a trusted american manufacturer such as Eagle or TAG. These pouches and kit will last for quite some time (My first piece of Tag kit just started to rip, and I have put it through seriously hard use for two years. It actually hasnt even ripped yet, it just started to fray on the bungee cords. A testament to its endurance.) Compare this to Condor gear, where I had a dropleg that ripped on me after my second use, nothing a little fishing line couldnt handle (superb thing for stiching btw), but still, the quality of it irked me.
Uniform wise, I would recommend getting Multicam or ATACS FG. Multicam is the more mainstream camo in the airsoft world right now (tahnks to Call of Duty), but also mostly because it flat out works in a variety of enviroments. ATACS FG is relatively new, but has a lot of potential if you ask me. Brand wise, I would say go with Propper Uniforms. THey will be your most durable/cheapest option. Tru spec uniforms are very iffy, sometimes they have problems ripping, and they definetly fade very very fast. I would stay away from them. You also might want to look into a blouse, pants, Combat Shirt option. The combat shirt and pants for the summer, the Blouse and Pants for the winter. IF for some reason you feel like you want to spend a lot of money on uniforms, then go Crye PRecision. They are very expensive (Combat shirt, elbow pads, Combat Pants, knee pads = $400) but they are extremely worth it IMO. The best uniforms on the market right now, currently used by special forces worldwide.
Headgear, standard ball caps can be found for as cheap as 10 dollars. Boonies can range anywhere from 10-15. That will be enough to cover his face.
Boots. Good boots are very important. Tennis shoes wil not cut it. Especially if you go to some of the larger, weekend long games. The terrain will be murder on your feet, and your going to wish you had spent the money on a decent pair of boots. Boots range anywhere from 40 - 200 (40 for a crappy pair, 200 for a nice pair). I like brands such as Merrel and Bellville, although they can be expensive. If your on a budget, go to an Army store, or a hiking/outdoor store, and try on several boots til you find a comfortable boot. You will be glad you did.
Last but not least is Eye-pro. Now any ballistically rated eyepro will do. Paintball masks, full seal goggles, OAkleys or Revisions. Again, it depends on your budget. For indoor games, I recommend having a set of Flakjaks and an Ironface. For Outdoor games, I reccomend some Oakleys or REvisions. These are the combinations I have tried that have not fogged up on me, but to each is his own, find something that works for you.
Hope this helps some.