As a Novice, you start out in the Town of Gnawnia, and the only other location you can travel to is the Meadow. Town of Gnawnia has a greater variety of mice, but in the Meadow you may find a Mole Mouse which dwells only there and in Town of Digby, and a Dwarf Mouse carrying Torn Pages of Plankrun's Journal.
Once you are an Apprentice you can travel to the Harbour. The recommended minimum trap for the Harbour is Mouse Trebuchet. In the Harbour you may want to purchase ingredients for Dehydration Base and other crafting from the General Store. As an Apprentice, you can only craft White Cheddar cheese.
Once you are a Journeyman you can travel to the Mountain. The recommended minimum trap for the Mountain is Swiss Army Mouse Trap. In the Mountain, you will need to catch a Ninja Mouse carrying a Burroughs Laboratory Map Piece. You may also collect Splintered Wood for the Dehydration Base, which is dropped by Dwarf mice.
Once you reach the rank of Master and provided you have the Burroughs Laboratory Map Piece, you can travel to the Laboratory. The recommended minimum trap for the Laboratory is the Swiss Army Mouse Trap, although you may also consider purchasing NVMRC Forcefield Trap. In the Laboratory, you will need to catch a Dwarf Mouse with a Key to the Town of Digby and a Zombie Mouse with a Tattered Mousoleum Map. You will also need to collect Radioactive Blue Cheese Curd Potions dropped by various mice, and prepare either Brie or SUPER|brie+ cheese to convert to Radioactive Blue cheese. In the Town of Digby, you will need to purchase one of the shadow type traps.