it all depends on the knowledge they have, if as a beginner it is easier for them to play casino, then you should use the casino as the first place to gamble. but for me, I prefer sports, because in addition to hobbies with sports we can also rely on luck as a container for our financial freedom. and it all comes back to us, which one is preferable, because gambling only relies on luck.
Casino games are more on luck while sports betting still have a chance to analyze and gamble not based on any luck.
This will always depend on your preference and of course as a newbie its your obligation to familiarize everything before putting a money, i believe that you can learn everything here if you have the will. I suggest to understand both casino games and sports betting, when you’re done you can choose on which field you want to focus more.