Honestly I never experienced having a referral commission because I don’t have any friends that want gambling and also I can’t post it on social media because I’m just attracting them to gamble and it’s my conscience if they lose. 
You have nice set of friends then if all of them don't gamble and maybe they don't also drink alcohol and smoke? But you are different from them. Didn't they figured it out that you are into gambling? Maybe not yet since you said you are scared to post any gambling related posts as your statuses. I have an idea. Why not create a dummy account only for this purpose?Friendships are in levels, it depends on the kind of rapport you've build up with your friend, some kind of friends have boundaries to what they can discuss or share as an idea, in this cade it is always go to understand the situation of things in other to avoid complications or bias mind with each other which may lead to having no trust on a fellow, gambling games has some certain target where if you want to tefer a person, you could easily achieve that as such platforms like the social media work pretty well with doing that.
Although I don't think if some social media sites will allow referral links but you can try using a link shortener.
Most do allow but few among them like that of close group dont give room for that.
I think there's also a site where you can legally promote your referral link but they are not free although they can be worth it once you got lucky and a whale gambler signs up at you.
Exactly, better to sing where your song will be acceptable.