Easy Gold

All you need is sagecraft 8 (If you dont have this use potions). For maximum profits get ranks in mercantile but it should work with any,

All you need to do is buy all the shards you can (Vendors are Rey kildeen next to ballads oratory, Brother Gamian in St Hadwyn's mission, Pell Grandy and Adept Jorum Quintus in the scholia arcana embassy in Ysa, Anker edmure in Edmire and finally Maeve Agrigal in Gwalchmai's goods in Rathir) Once you have done that sleep for eight days and repeat till you run out of gold or decide you have enough. On your final round go to rathir last and once you have bought the shards strengthen them till you only have pristine(This can take a while). Craft all those shards into epic gems then drink a mercantile potions if you have one and sell them all to Gwalchmai.

Through 5 rounds of this at 6 mercantile, 8 when selling (You dont need this but you wont get as much) I got over 2 million gold.

I dont know The best shard combos, if other merchants give more gold or if this works with a mercantile skill under 3 but I hope this helps you.