If you are playing mage, then you're going to need to do some "sneaking" around first. At least until your intellect is higher and your spells can make up for your low leadership.
After you get to the Scarlet island do what you can there, dodge the enemy patrols and pick up all the leadership flags. Also visit the small shop on the right of the castle. The quest from there will give you a map to find 2 chests. You can get these without fighting if you're fast.
Then go to Bolo island. If you sail west to the smaller port, quicksave and time your run well, you can run in and grab the map for the Anchor island. Once you have it, travel to the Anchor and you can complete the chest quest to the right of where you first arrive for a good EXP boost. You can also see the pirate on the beach to the left of the start area and do his quest to find the bottles. You will get a big EXP boost and a random artifact. There are also some flags here you can grab if you dodge the patrols.
Then you should have enough leadership and runes to do most of the battles on Scarlet and Bolo and you should be ok after that.
