Well, seeing as you're new to airsoft, you're conclusion is totally understandable.
But the unfortunate fact is you went the wrong way about this....
You WANT a good base to start with. A REALLY good base. Not necessarily expensive (the KA M4s are amazing and inexpensive). But having a poor base will affect your internals no matter how good they are.
Just like a car can only ever be as good as it's base. Putting $1.5 million of upgrades into a honda civic will not make it a $1.5 million williams F1.
And upgrading the crap out of a chinese mechbox is like getting maybach to upgrade engine block of your chevy aveo lol
So having an inexpensive gun is FINE to start with, have fun with it. But if you plan to fully upgrade a gun, you may want to get a KA or G&P M4.
But there are things you can do to get the best bang for your buck out of your starter gun;
upgrade your hop rubber
make sure your mechbox seals properly
shim your mechbox correctly
put a new piston head in if possible
use the proper weight of BB for your FPS
These simple things will get some really good performance out of your gun, just don't go spending $400 on a full tune up kit because you won't likely get a $400 difference out of it