Accurate ADC reading with Bluepill

Hello all,

for my DIY Radio Controller (LoRa and STM32F1C8) i am using two joysticks and one poti.

I am reading ADC with the DMA but what i noticed is that the ADC values are not so accurate.
I know with not (professional, expensive) Potis and joysticks this accurate is almost impossible.

With 12 bit resolution the ADC value is (0 - 4095) but the problem is that sometimes the tolerance gets more then 20 or 30 and this value is not ignorable for RC.

P.s. the wires from Joysticks and poti are about 10cm long.

My question :

Is there any idea or way to get more accurate readings from ADC? some filtering or anything else.

Would be using switching regulator as Vcc problematic? 

Please if you have some tipps or ideas it will be appreciated.

Thank you in advance.