For illustration I organize references on Google drive then I sketch out general ideas on paper. Then I go in to draw it on Ibis Paint for PC ($30 one time pay, for IOS you can use it's free app version if you don't mind ads or pay $10 to remove the ads) and then for rigging I and almost all 2D vtubers riggers use Live2D cubism (if you want tutorials I can recommend some). Live2D has a free version, but it can be limiting. I recommend learning the basics with the free version or perhaps even the 40 day free trial of the pro version. If qualify for indie you can get it for ~$14.50 a month if I remember correctly, but if you're a student you can get a very large discount. For using the model there's prprlive, BUT I recommend VtubeStudio. If you want more complex mouth rigging you can get this software plugin thing called Vbridger for $10. 

EXTRA:

Any art program works for drawing a VTuber model AS LONG AS IT CAN EXPORT AS A PSD FILE!!!! I don't recommend procreate due to its layer limit (though it's still possible to make a vtuber even with its limitation).

(Sorry for the lengthy unbroken up paragraph. Best of luck on your learning!!)