If your in it for less cost, you should fish while cooking, because you get more EXP for cooking fish meals from the fish monger recipes. As for leveling and exp I would suggest if you spent anything buy wisdom lixes and work on your ability first it will save you money in the long run since to be really profitable for like the fruit salads/casseroles and brith's you need around 1,400 to 1,500 cooking proficiency
I leveled first and did mastery after It sucked big time. I would recommend going ahead and maxing mastery out and then continue leveling it since it seems to re max itself every level for me so far. This would be cheaper and easier than picking thousanda of oats for it when the time comes.