I have a few criticisms in d-boys. such as plastic bushings and on and on.
However the D-Boys SPR (which Im assuming is like a M4 variant?) would be decent for starting out and doing some backyard type airsofting.
For the battery the max I would reccomend is a 9.6v and no higher. It is imperative that your gears are properly shimmed or else you will start stripping gears, even with a 9.6v.
Of course it is going to be a plastic body so that is a con, but you can always buy better latter on.
The SPR's accuracy is only going to be so-so even with a .25. Remember you don't have a TM hop up in that gun.
Overall D-Boys is a 'fair' gun for the price. Make sure you take good care of it and it should last you. Some tips:
-Clean the barrel regularly after every time you go thru 2 mags
-Buy a case to protect the plastic body from being damaged <this goes for full metal too, you don't want to scratch that lovely paint off
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-If you do buy a 9.6v. also buy a simple smart charger ,~$30, to ensure that the battery lasts longer than the $50 you paid for it.
-Keep the gun in a dry location, preferably a gun safe w/ dehumidifying equipment. You can also wrap the gun in a old towel and store it in a bedroom closet away from water closets and bathrooms.