2d12 means that two 12-sided dices are rolled to determine a value. In other words, the value can be anything from 2 (1+1) to 24 (12+12). 6d10 would be rolling a 10-sided dice six times (value 6-60).
Assuming you have maxed out start money: Buy Lv 2 and 3 ship, buy Lv 4 and Lv 3 chest to max out loot and magnet (8), then buy Lv 4 Weapon. Next save up for Lv 4 ship which you should be able to buy in Stage 2. Don't miss the treasure chests. Before Stage 2 boss, buy Lv 3 Sail, you'll need it. With this setup you should be close to 5k before Stage 3 boss. If you are, buy Lv 5 ship right away and try beating the boss with this setup. If you do, you should be able to buy all Lv 4 items.