Synths are a bit of a jungle and it's definitely possible to get ripped off.
Don't assume more price = higher quality, doesn't hold true IMO.
Once you start to learn sound design you'll see that different synths have different methods for generating sounds, some have more/different options. Some people consider some more user friendly (I haven't noticed much difference personally) some claim to have higher quality sound (Either cleaner digital sound or analogue emulation)
I would say learn your stock synths then make a decision for yourself, but tbh most modern synths are good these days.
Try randomly picking one from this list and you won't be disappointed:
Serum (Current favourite amongst sound designers)
Zeta 2+
Omnisphere 2 (lots of good stock sounds)
UVI falcon (very new, hasn't made a reputation yet but looks great)
Synthmaster 2 (the synth I own, got a nice wavetable update recently)