Three basic 'Forms' of airsoft guns:
#1. Spring powered.
#2. Electic Powered.
#3. Gas powered.
Those are pretty self explanetory of how they work. Since you want an electric gun I'll go more into depth on your questions and them.
With the magazines,bbs, and other stuff it's gonna run you over $200 USD if you want an actual good gun.
Overseas site:
www.uncompany.com (Huge selection! hipping shouldn't be too, too much.)
Best site located in US:
www.trinityairsoft.com (Some of the cheapest prices you'll find some airsoft guns in the US.)
If you want an SL8 DON'T ever buy a conversion kit as they are rip-offs. As for the orange tip there's two things you can do:
#1. Buy a black flashider. There is also orange ones incase you take off the whole tip. There isn't flashiders for every gun but just look around.
#2. "First you have to file some paperwork with the FBI, you can send them an email and they will send the proper forms out to you. after you fill out the forms and they contact you about the removal of the orange, they will send you a special can of spraypaint in the mail. it's special flat black FBI spraypaint, the same kind that they use to take the orange off of their guns with down in quantico.
once you've sent them all the proper forms and painted the end of your gun, they will also send you a card saying that you have been authorized by the FBI to remove any and all orange from your replica firearm. all you have to do is show the card to a cop who stops you and he will just give you a warning and let you go on your merry way.
should you remove the orange without proper authorization you risk severe criminal punishment and/or fines. the BATF will be coming to your house to confiscate all illegally altered replicas and you place anyone in the house at risk for prosecution. by federal law every gun coming into the united states has a tracking chip in it that allows it to be tracked by various law enforcement agencies, so if you think you can remove the orange and "they'll never know"--you're dead wrong!"
NOTE: Copied and pasted from the old airsoftretreat forums from Atilla's profile.
Since you said 'Gas Rifles' as an option lemme tell you something. Those guns are called 'Classics' they are no longer in production. Though you can buy them off E-bay, airsoft forums etc. They run off of tanks of gas (obviously). I don't know too much 'bout classics so I'm not really the guy you should be talking too. There are electric guns in your price range two of them:
#1. AEGs (Automatic Electric Guns).
#2. LPEGs (Low-Powered Electric Guns) LPEGs can still shot 270+ FPS so they're still pretty damn decent.
The basic supplies you need for electric guns are:
#1. The gun (Dur!).
#2. A battery and charger.
#3. Airsoft BBs (Preferbly .2 gram as .12 gram and under can jam it because of the low weight.).
That's all you really need to start out. Yes there are way more stuff you could get.
Here's some shopping tips for on the internet:
#1. Know what your buying.
#2. If you see a gun that has a descreption too good to be true (Ex. All metal and wood. That kind of shit would run you $300+ for the whole thing.) and a low price. 99% of the time the gun is shit and will break on you.
#3. Don't buy stuff from sites that have guns that look 'cool' and have low prices. Again, probably most of the guns are shit.
Well that's all I can think of. Here's are some sites just for reference:
Airsoft Forums (that I use):
www.airsoftretreat.com (Really good site!)
http://arniesairsoft.co.uk/forums/ (Be careful these forums aren't modded well and get crazy at times!)
Last, before you buy a gun:
#1. Research your gun! (Read reviews, find out what you need to buy, etc.)
#2. Find a place to airsoft. (My favorite especially building bunkers and stuff.)
#3. Last if you want to play games first MAKE sure some friends have an airsoft gun. There are places you can go to airsoft to play against people.
Yes airsoft guns CAN be upgraded. Well, if you have any questions just PM me, email me, x-fire me ,etc.
Hope this helped!