Hi mate , if you buy a ready to fly it will most likely come with cheap parts , unless you go for a really great make but it will not be cheap, if you build your own you can control the price of parts BUT you will spend as we all do on better parts than cheap one ( buy cheap buy twice)
Now as for stable most FCB have a stable mode built in you just switch it on and off even the cheap kk2.1.5 has stable mode , top of the range naza can have auto take off, height hold, GPS hold, return home mode etc .
The hardest thing to work out is motor and prop set up? what battery ? what flight time etc , this will help www,ecalc.com
one more thing basic quad needs 4 channels but if you want lots more thing on it like what the naza has then your need more channels so you can turn them on and off