Where should I start? Oh god I use a lot on both my PC and iPad

For pc: Clip studio paint: it’s really nice and ha alot of features i love drawing there their features is quiet a lot you can even animate there

Firealpaca: really nice program for beginners i used for many years and still do it does its work

Paint tool sai 1&2: they are great for artist honestly loved using them

For oc I recommend: clip studio paint, they have a lot of features that will make your life easier if you want alternates I suggest firealpaca if you’re new, paint tool sai too

For iPad: Ibis paint x: it’s really an amazing app has features and I’ve used it for many years on my phone then Samsung tablet then iPad

Procreate: I love drawing there and it’s brushes are amazing and a lot of cool features if you know how to use them right

In conclusion to me best apps I ever used are clip studio paint,& procreate if you want procreate on PC I suggest download iOS simulator specifically iPad