This.. I am f2p player, only t3, t4, and now (last update) t5 daily quests are the best way to get gold..
But I have second way here. When event spring, horror, and any event come, you can get more gold for farming many thing there, and the dungeons one..
If have much gold, f2p player can invest gold for crafting or reselling items..
I've been playing for 6-7 months and now max level character and have 2 crafting professions that reach lvl 15.
So good luck for f2p player.