Yikes, no.
If you can purchase currency with Robux, use Robux to manipulate currency, or anything along those lines, absolutely, positively not.
Just like @Timelens mentioned, you shouldn’t really be getting into gambling games on Roblox, since it’s a real gray area, even if you follow the rules.
Understand that eventually and gradually Roblox is trying to move into the market of having an older audience, but in the meantime, there is no reason to give younger children potential gambling addictions.
If you want to make a gambling game but still want to use Lua, I would look into other Lua-based engines such as Corona, Love2D, and Lumberyard.