We need to remember that the idea of the perfect man that Kipling presents us with is very much a product of his culture and times, which in some aspects is very different from the way that we would think about what a perfect man would look like in our times. One of these differences is the way that gambling was a very socially acceptable passtime for men in Kipling's day, and it was expected that you would gamble. Thus it is that in the third stanza, part of Kipling's definition of a man is based on the nature in which you gamble:

If you can make one heap of all your winnings 
And risk it on one turn of pitch-and-toss,
And lose, and start again at your beginnings
And never breathe a word about your loss;

Far more important than focusing on the gambling aspect, however, is being aware of the ideas and values that lie behind it and the kind of characteristics that this description points towards. Gambling is not the issue here: Kipling is using gambling as an illustration of the kind of daring and risk-taking that is often necessary and also to give an example of fortitude shown in the face of adversity. The outward trappings of gambling is therefore used to present us with the inner qualities of manhood which is shown in the ability to take risks and then to not complain or moan if those risks result in you losing.