Very Rarely you will get good drops out in the world(unless you have a high monument and high alchemy stone) So relying on drops isnt very efficient,the best way is to get throw away orange gear with 1 slot(keep it for yourself if it has 2. Also make sure its not used in upgrading your gear at the blacksmith) and yellow gear from Shakatu that has 2 crystal slots,then turn around and sell those in the market. Keep in mind you can only sell 5 things a day in the market so you cant really take advantage of making a TON on silver in the market unless you sell really good orange/red items but i would keep them for yourself. So if you get lets say 5 crappy orange items and sell them for 15 million silver a piece you can make 75 million silver a day. Not too shabby if your stuff does sell but most the time it wont sell on the first day.
So i wouldnt really rely on this sole method of making silver. You can use it in conjunction with afk farming. Usually what i do is either do the spellbound trick http://blackdesertmobilehelp.com/knowledge-base/selling-soulbound-items/ or get items from Shakatu to sell while im afk farming.