this is the thing with mining, unless you have all the mining gear it's really a gamble to mine. all areas you can make good money. but take bastok for example, you can get color rocks, platinum ore, Darksteele, pebbles, broken pickaxes, iron ore, copper ore, silver ore, gold ore, platinum ore.
in bastok the average stack of pickaxes will be anywhere from 2500 - 3000 a stack sooooo if you take one stack in there and come out with just one colored rock you make your 3000 back, if you get two colored rocks you make 3000 out of the deal, if you get one darksteele ore, you can make 7000 out of the deal, now granted in bastok mines the chances of the higher level things are much less likely than if you were to say mine in gusgen mines or palborough mines but at your level it's probably safest to say bastok mines becuase there is the possibility.
Pickaxes are strange without a suit, you can break as much as 6 pickaxes before you even get a pebble or you can get 4 darksteele and not break a single one, it's really a gamble, with the mining gear, it decreases the chance of breaking pickaxes considerably, so you can go much longer and make the pickaxes work for you rather than just blowin 2.5k on absolutely nothing.