Upgrading my CM16 Raider
 

In what way would it be good to upgrade? Get new bearings and a 6.03 inner barrel?

Budget is looking to be around 100-150.

Please give me suggestions!

Sell and buy a gun with a metal body ?
The polymer one is fine if you wanna go for an ultra lightweight setup.

What to upgrade really depends on what you want to achieve. That said replacing only the bushings/bearings won't really yield much of a performance increase. A 6.03 inner barrel should increase your FPS slightly but won't really do much for your accuracy if you don't get a quality barrel. A quality tightbore like a Prometheus or PDI will run you pretty close to $100 or more after taxes/shipping.

After buying any gun the upgrades I would do would be:

-Shim job
-AOE correction (G&G V2 gearboxes are prone to cracking from my experiences) and sorbo
-Metal hop up and bucking, although the G&G green bucking is pretty decent
-Fix any and all air leaks

These mods will be very well within your budget and will definitely increase the longevity of your gearbox.