If you don't know what aspect of your gun needs improving, you don't need to upgrade.
We have a little saying in airsoft: "When you're ready to upgrade, you'll know."
Wanting to upgrade just for the sake of upgrading is, quite honestly, the worst reason to upgrade.
"Someone in a Prius tried to race me at a stop sign the other day. I couldn't believe it. I had him for the first 100 feet or so but I can only walk so fast."