It totally depends on the level of risk you can take to afford if you are high risk taker then sky is the limit in winning or else your earning becomes limited but nothing is guaranteed.
The higher you put money into gambling then the higher you might win but still the chances is 50/50,well some people are really luck that they win big some are just out of luck.
Isnt the 50/50 remark a bit skewed though.
Since there is a house edge for most of these games like dice its like 2% or something like that.