Many programs offer an ability to create designs, whether it’s art ui vector designs and more. Gimp krita paint net are your best choices since they both provide options to create a variety of artwork, of course these programs do have a learning curve and you will most likely learn the ropes if you practice.
I’m no digital artist. You could always research these specific questions as it will result into viewing many art programs it can be hard to choose a specific app. I’ll try finding a program that your comfortable with learning, I wouldn’t consider getting paid programs since most of them produce exact designs in any art app.
Hello! I do digital art and i use Clip Studio Paint! It’s expensive, but it often has 50% off around holidays! But if you don’t want to pay, i recommend Paint Tool Sai (1 or 2) or FireAlpaca! You usually have to pay for Paint Tool Sai but there are lots of tutorials on youtube how to get it for free. I also think MediBang is free, but I have never used it so im not sure.
Good luck on finding a good art program that suits you!!
I would recommend in the long run you use Gimp (or Photoshop) and Inkscape (or Illustrator). These are both free and are really powerful. Inkscape is more vector based, while gimp is not.