early game you can make money selling animal skins & meat, either run round looking for deer, horses, hares & wolves (if there's wolves in the area look for the red crosses on the mini map as they'll be animals killed by the wolves that you can loot) just use igni on the deer, horses & hares as it'll one shot them plus you're not degrading your weapons, you're not in combat so you don't need to wait for it to recharge, or you can go to the area near the inn in white orchard, there's a merchant (the fella with the bowl haircut you save from the griffin) near him are a couple of cows and a few geese, kill them with igni and loot them then sell the stuff to bowl head, meditate for a few hours and rinse and repeat
if you've beaten the griffin and opened up the other areas go to Novigrad (don't bother getting the pass just swim over) and look for a large square, you know when you're in the right area as you get a cut scene of a couple of people being burnt, there's a merchant in this area with a fish stall, buy all the shells and sea shells, you can just back out to the dialogue options then check his items again as they restock instantly no need to exit fully out or meditate, then look for an alcove with a blacksmith's stall (it's near the 2 fires) get him to dismantle the shells which gives you pearls & black pearls, sell as many as you can to the blacksmith then meditate to refresh his gold, there's also a loan shark
here who doesn't pay as much as the blacksmith but his gold replens a lot faster, i've made about 15k doing this