How can I generate and setup buttons via code

Maybe look into the other gui elements you say you haven't used before and see how they work? There isn't a single objective way, you have to use whatever feels best to you. T$$anonymous$$s is how innovation happens! You can learn to create buttons in script here. T$$anonymous$$s is sort of an old, but not wrong, way to do it.

I t$$anonymous$$nk with the more recent(not really recent) GUI design system they implemented in Unity, the workflow is to build the gui in the editor visually, make it a prefab, then referencing the instance of the prefab in your logic. I'm assuming that the characters have the same amount of abilities as each other since you said you were using an Array and not a List. If the characters have different amounts of abilities from each other then you will want to use a list. If that is the case then you might like doing it the old way. If they all have the same amout of abilities, you can add the button components you need manually and then use their OnClick events on their component in the inspector to point to any public methods you've made on the character class script. Even if the characters have variant amounts of abilities, you could just disable the buttons that aren't used for that character from your script. Use a Vertical Layout Group to line your buttons up together, btw.