Krita is really good if you're on a budget since it's free. I really like Clip Studio Paint. That one is $49.99 USD, which is more expensive than I remember it being, but I may have got it while they were having a sale.
I'd recommend Krita https://krita.org/en/ it's free and it has everything you need from drawing, paiting and animation it very customizable, I've been using it since I started doing digital drawing back in 2018, if your son wants to make comics there's even templates from all different styles and the animation workspace is like a classic frame by frame. It also being constantly updated with new features too.
You should check out Krita. It's free and emulates traditional art implements.
You should also get yourself a drawing tablet if you don't already had one. Drawing with a mouse is horrible. Wacom always makes good ones and you can find them second hand if moneys an issue.
Also lovelytrout's suggestion is a good one, YouTube is the best place to pick up digital art techniques.
I was looking into this last night, a few brands seem to get recommended as alternatives. Here's two common ones I found after some digging, haven't tried either of them personally but this is a good place to start your research
Amazon Links:
Hello!
I've recently purchased myself a tablet with a screen on it (a Wacom Cintiq) and I've been very happy with it! Wacom tablets will always be the top of the quality chain as far as graphics tablets go, but unfortunately they are very expensive. Wacom is of impeccable quality, though, and is definitely worth the money!
Luckily, though, there are alternatives for screen-tablets, but I haven't tried them myself so I cannot testify their quality (buy at your own risk). It's definitely going to depend on your budget, as well, since screen-tablets can go for anywhere between $500 - $3000. I'll post some links to Amazon products below.
This is the standard size Wacom Cintiq: Click here. Its screen is 13 inches, and offers great quality on Wacom's cheaper spectrum. At $800, it's still a little pricey, though.
This is a good alternative, the Ugee 19-inch screen tablet: Click here. The reviews on this one are quite good, and at $430 it's definitely much cheaper than the Wacom.
There are a few variations on Amazon so you can check out a few more of them. Please do make sure you look up plenty of reviews before deciding, though! You don't want to skimp much on screen-tablets, because you really do get what you pay for. Good luck!
I am planning on getting this one https://www.amazon.com/gp/product/B01E0LJD0W/
I like to draw on my phone because the touch screen lets me easily zoom in and out, and its easier to draw on a smaller surface.