[Dwosky]

For a 350FPS or lower replica, either the NiMH or a 7,4v LiPo should work correctly.

Regarding LiPo brands, I usually go for Hobbyking's Turnigy ones, since they're decent for the price they cost. The size (mAh) would depend mostly on how much you pull the trigger. The limitation in your case might come from the fact that not all batteries will fit inside the G&G's CM16 Raider, so I would suggest to first measure up the space and then find a battery that fits it.

 

[Dwosky]

Thanks for your replies, guys! I ended up with G&G FFR A2 with 11,1 v

Does that replica have a mosfet installed? If it doesn't have one you will suffer from trigger issues as the contacts start to wear off due to the electrical arcing. This doesn't mean that doing one shot you will kill the contacts, but they will gradually wear off.

 

[Dwosky]

I have the IMAX B6 Mini and from my point of view it does the job without problems and should be under your 30 euros budget. Just make sure you get an original one, since I've read some post of people having issues with the copied ones. The originals have a sticker with a serial number that you can check for verification in their page (http://www.skyrc.com)