First, make sure you have a Supreme Pickaxe. For 3,000, it's a pretty good investment as long as you always keep an eye on the durability of it. Then, follow these steps:
1) Exit Town of Amarance and go to the map left of it.
2) There will be one Mountain Murdoc on that platform and a mining rock. Kill the Mountain Murdoc for a bit ofexp and to get it out of your way.
3) Mine the rock and get the items from it.
4) Return to town, rinse and repeat. If the rock does not appear when you return to the map, return to the town and go back. The rock should be there again.
From killing the Mountain Murdoc, you may get some decent equipment and gold, along with some Deluxe Spice Sets, which sell for 400ea. From the rock, you will get mostly Thorium(which sells for 250ea. It may not seem like much, but you get a lot of Thorium), along with some other stuff like Emeralds(which sell for 300ea), Sapphires(which sell for 400ea), and Diamonds(which sell for 200ea). Repeat this until your axe goes down to 10 durability, and then go to the Amarance shop, sell the ingredients, and repair your axe. If you have followed everything correctly, you should be getting about 10,000 or (probably) more from this method.
Exploiting the Execution Room and the Campfire Quest:
The Execution Room, which is new to Zenonia 3, is a very simpleway to level your character early in the game. Once you get to the town of Delfoy, do the little side missions and a couple of the main ones until you get level 10 or higher. This wont take long if you are adamant. Once you can at least clear one room you get about 2800 XP and a very nice (albeit random) equipment that is usually magic or above classed. The equipment that you get is a level or so above you which will give you something to work towards. You will die plenty of times, but don't use any origins of life unless you have enough of them or plenty of Zen on hand. There is no penalty for death in the Execution Room; you just get sent to the very first room and you have to clear it all over again. The monsters and mini boss legendaries that you fight will be randomized each time you enter a room, so don't expect a "watering" creature on the first floor every single time. You may have to grind it for a while to fully exploit the room, but each room cleared stacks XP and that gets to be a pretty big amount for just a couple rooms cleared, which can get you a level or two in just a few minutes if you play your cards right and heal when necessary.