I've read some posts about people having trouble getting their gold after they buy it. Looks like everyone eventually gets it, but I want to make it easy, so I'd like some advice before I buy.

I am a steam user and a signed up with the friend invite. I recently hit level 50, and I got no gold. I thought I was supposed to get free gold when I hit level 50 and again when I hit level 80. Maybe it only applies if I use my coupon to buy gold. So I want to buy some gold, get my 40% discount and my free level 50 gold. What is the best way to do that?