We have all witnessed many players in our maps use Gold Marks (GM) and I have personally fought many players which seem to have deep pockets. This is not limited to the big 500 and 100 p maps. I have seen new players 'spam' arty and cruisers on day 8 and planes on day 10 in 31 p maps. So, to help the community I have listed what are a few ways in which you might best use your own GM, or ways in which might simply be a waste of this rare and valuable coin.
When fighting , I have many times accelerated airfields using 850 gold as a means in response to a player burning down my provinces airfields to keep my planes out of range. The concept is to build lvl 1 & lvl 2 workshops then to accelerate the airfield, which costs the opponent another 8,000 - 12,000 gold to burn down airfield again. So, you spend 850 gold, forcing opponent to spend 8,000 - 12,000.
Calvary units > Day one in a map spending gold on 10 cav units is about 18,000 gold and would be a huge advantage.
Instant Gold Spys > Prior to a war against an opponent , it costs 750 gold for instant spy to reveal Country information
Reveal Armies > once at war with someone it cost 1650 to reveal all countries armies
Healing Mech Units> Planes and ships are expensive and very cheap to heal, saving resources and time to rebuild
> destroying opponents infrastructure/buildings
> healing huge stacks of inf,
> accelerating production of mech units
Plan your own gold use, use it strategically and tactically, with knowledge that there are many players that hope or plan to win simply by using GM. Although frustrating at times, these players are not to be criticized for their use of GM, as they are supporting the game expense and keep it free for the vast majority of the players.
If you plan properly and use your own gold to benefit your own country you can achieve greater success than to simply retaliate. I know from experience after many times fighting such players, they will quickly become familiar with you and befriend you rather than fight you while using these strategies I have mentioned