Congratulations. I only changed the batteries to 7.4v LiPo with deans connectors, and left the rest as stock. I may upgrade barrel and hop rubber next year but it works well enough and so no point replacing parts this soon. It may not shoot as far or as fast as other guns, but it is a thing of beauty.
I have purchased a foregrip, rear sling mount, sling, flashlight, rail covers, scope and scope protector, but apart from that it is just as it came out of the box. Have added one hi-cap and three low-cap magazines, and using Blaster 0.25g BBs.