By beginner snake, it depends on if you mean easy to handle/docile temperament, or undemanding about their setup and husbandry.
I'd recommend dumeril's boas, one that's at least 1-2 years old, for something that'll get much bigger than a ball but still manageable. Undemanding husbandry, and very docile and calm. Males are smaller, females can get 7-8 feet and thick.
For colubrids, definitely a russian rat snake! Big and docile and easy husbandry
If you really want a species of carpet or bullsnake, do your research on their temperament first. Not all are docile lol.