Glocks are always a good choice. The Marui clones (and indeed the Marui ones) are great and easy to find parts for. They're generic, but they get the job done.
As for CQB, gas is a good bet because of the trigger respsonse. Springers don't fire fast enough but lots of people get by with the springer tri-shot shotguns. AEGs are fine too really but you might lose out on those corner shots if you're up against someone who can fire a bit quicker. In reality though you'll probably just trade kills.
You can certainly get by in CQB with an AEG if that's what you're asking. When starting out, dumping money on a pistol is almost always a bad idea because they're not very versatile and can be pricey (magazines and gas). If you've not got an AEG then get something nice and generic if you're not sure what's best and then you'll always have something to fall back on if you find that the pistol/sniper rifle you think looks cool doesn't work out for you.