Hey welcome to the community, for now i suggest just making your way up in levels. Gold is much easier to get on the higher campaigns than on the lower ones. Alien Oasis is a good place for gold especially the level 'Plasma Pyramid'. If you want to make gold faster remember to do the levels solo. If you don't all of the gold is spiit among the players. Once you hit 50 and have done most of the quests then you should have a good lump of gold. Hope this helps!!