Well first of all i would like to inform you that weather you do trading or gambling both are too risky.
First different is investment. Now till now in trading i only found iqoption which allows minimum amount of 10$ required while rest all have 100$ as minimum deposit.
On the other hand in gambling as far as i know the minimum deposit is 0.5-1$ not exactly sure.
Second trading is really risky compared to gambling as for trading you need skills and brains while in gambling you don't need any skills it's mostly luck.
So all the people who simply want to try and have no skills then i would recommend you gambling others who think they know a bit about stocks and stuff then trading would be fine for you.
Hope it helped you in deciding which is better.