How can we make gold faster?

Playing maps or player shops?

Probably fastest way is to farm c1 to c3 to get plain motes.   They sell for a minimum of 1 million per 99 stack and more if you are lucky.

Play maps definitely. Dont worry about the gold at all. It isnt really relevant compared to the loot, shards and xp you're missing out on just by optimizing your gold farm, you still get a sufficient amount of gold just from doing maps, maybe try not to spend it all on unnecissary upgrades, markets and shard gilding to start out with ;)

Play C7. If you have Wpn Manus (2-3 nodes) or a strong Flame Aura or Fissures with the exclusive Servo and strong PDTs (max rate especially), you can slaughter most of your opposition in seconds. A win here is about 55k or so without APx or Streaks (I am on AP5 and I get nearly 90k with max streak). As your Gold multiplier rises, you will net better rewards and it becomes bountiful when you start farming your own Motes.

You can also sell your junk items that drop. Legendaries with crap mods can shoot up to near 2.5k-3k. A game can net you about 20-30k in item sales if you sell all gains. You should also open any Pet items and sell them when you hit 99 of it when your pets are finished.

If you find a good mod with a good value, you can sell the item to a player for a reasonable price. 

There are also Defender Packs as you complete Onslaught. If you end up getting an accessory, skin or hero you already have, you automatically get gold ranging from 155k to 1.55M. There is also a chance you can get a piggy bank for up to 5M. 

Also, if you are using Gold to Gild shards, try to combine them with medals (either to max the shard or pay the gild cost) so you can burn less resources. A worst case scenario is about 2.8M Gold to gild a 241 medal/573k shard.

If you combine these strategies. Gold becomes a joke to gain quickly.

The fastest way to get gold is to do AP resets so that you start stacking the +5% gold bonus you get for each reset.   To put it in perspective, someone above said that their max win-streak gold from each map is 90k/map.   With my current resets, my max win-streak gold is around 250k/map.   It takes time to accumulate the +5% gold bonuses, but you will earn gold significantly faster by resetting and then playing maps.

With that said, I can assure you that (after stacking your gold bonus) it takes a lot less time to farm maps for gold then it does to sell materials.