Cheap / Upgradeable / Decent looking.
Pick 2, at best.
Anything cheap & decent certainly isn't upgradeable.
Anything decent looking & upgradeable is not cheap.
Anything cheap & upgradeable......... either doesn't exist, or will not look remotely appealing.
Most laptops use soldered CPU/GPU or one or the other etc.
There are some laptops using desktop CPUs; but GPUs are usually a different/custom form factor and a standard cards (say a GTX 760 from EVGA, for arguments sake) will not simply "fit".
Without knowing what CPU/GPU/RAM you have, it's impossible to say for sure........ don't even know what era of laptop you'd need.