We can always try our best to make sure that our kids have the best that they want in life, and we can also try to restrict the kind of information they get their hands on, but we can't completely control that. Just as you have outlined, the use of social media makes the parental control job a little bit difficult.
Even if you try to reduce the amount you allow them to have access to for their upkeep, if they still want to spare some that could be used for gambling, they can still do that as long as they have time to go out and mingle with friends. Everything can be made possible.
Depends where you live. In my country kids can't play with slots, lotteries, and even online they would need to commit and identity theft, which isn't easy to pull off, and even harder when someone is a kid.
I have 2 kids, and it's never easy to controll what they see but they still don't have social media and i wouldn't even allow them to have that before they are 18. I might seem like over controlling, but when they are adults they have time to be responsible for themselves, but before that, i am responsible and i slowly grow their responsibility on what's appropriate to their age. Kids need limits from adults, otherwise they are burdened by trying to set their own limits, even though they aren't mature enough for it. All because parents were too busy to take care of it, or too lazy, or just didn''t care.