It's definitely not hard coded levels, as you can do /setlevel 1000 then /respec to get a load of the things, and increasing your level even more gets you still more of them. It feels to me like it's every 3/4 levels after you've reached level 6, or something similar. The only fact I know is that you get your first gold point after exactly 6 level ups (so from level 1 to 7), and you definitely max out a skill before you reach level 30, so it can't be every 6 levels.