Dungeon running is the best and fastest way to make gold. You can make about 20-30 gold/day by running AC P1/P2/P3, COE P1/P2/P3, COF P1/P2, SE P1/P3, TA U/F and HoTW P1. If you have no experienced with one of those dungeons, don’t be afraid, just post in LFG that you are new.
When you have more gold, you could invest it on some skins/items that dropped/loot from one-time event. Those skins/items price are always expected to increase rapidly in the future. For instance, when the dragon bash event released, I bought 20 dragon wing skins that cost only 8g/each. Now its price is up to 22 to 24 gold/each on the Trading Post. Moreover, when Zephyr event released, I also bought 10 Zephyr Rucksack Skin that cost about 8-9g/each. Now the price of Zephyr Rucksack Skin is increased dramatically to 40-45g/each on TP.
Another way to make more gold is doing world boss events. Every world boss drops about 1-3 rare/exotic. You could salvage rare items for ectos. For all exotics, if it costs more than 1,5g on TP, just sell it. Otherwise, salvage them.
Addition, killing champs in Frostgorge Sound is also a good way to make guild wars 2 gold. I haven’t tested this but my friend said that he made about 40-60g/day by following this method.