This seems to suggest that if you spend more money you may advance faster. SHOCKING !! WGT will reward you for spending more money !!
The "reward" = tier promotion comes from WINNING credits in tournaments and matches and from WINNING matches against higher tiers.
I'm not sure, it depends what wgt think of as "winning". If I pay 100c to enter a rg and my placing in it means I get 100c wgt congratulate me on "winning 100c". Of course I didn't, I just didn't lose it this time.
As I like playing rg's I enter quite a lot of them and have a decent amount of earnings, I still need to top up my account every now and then to keep playing. What I'm meaning is, it's probably true I'm buying earnings/winnings.
I would add I've never been promoted other than by ave and rr's.
Similar with matches against higher tiers unless it's measured by win %, which I doubt, the more you play the more likely you are to win some.