Probably depends on your goal. Do you want to get popular with your videos? Or just have a small platform for your content but the quality is not important? The good stuff costs a lot of money.
Avatar
Super cheap would be a basic .png that lights up / moves when you start talking. It gets used as placeholder for other Vtubers in videos usually.
More expensive would be a Vtubing model, there are free ones, if you want a custom one you might look at thousands of dollars though (Design + rigging).
Or you go with a VR solution (like VRChat and picking a model from there), content creators do use this at times and it’s free (if you have a VR headset, otherwise your movement would be too limited to be engaging).
Something more generic might be a service like www.animaze.us where you just pick an avatar.
Voice
This one is tough, you can use a full on text to speech solution, but then you have to type things out. Or use voice to text to speech (You talk, text gets written down, then put through a text to speech solution again).
Or you use voice filters, plenty of software for that around.