In my Own opinion?all of the mentioned gambling are Luck based games though some can be consider as skilled base but of course it is luck that will let us win so basically all are relying in luck and not skills.
Except card games I am not sure any other gambling games require any skills. Almost all of them are luck based games. Initially you can use your skills to control the game but eventually the house takes over and only luck plays. I have tried many techniques and skills but most of them won't work after some time.
card games can be used skills if in Real life gambling but in online?i don't think there can be skills or strategy when the computer is dictating what cards can be yours and there is no chance to check the faces and reactions of opponents.