Link 1 (TopG) lets you vote every 6 hours for 5 gold.
Link 2 (XTremeTop100) lets you vote every 6 hours for 2.5 gold.
Link 3 (GTop100) lets you vote every 24 hours for 2.5 gold.
you get 10 gold every 24 hours if you vote on all three vote links.
if you vote more than once a day, you will get 7.5 gold. This is intended, and has been like this for years (since 2013, if it has not been around longer than that.)