The above poster's third point is very true, you should jump on a boat as soon as you can (there is a boat for free) and cruise the maps picking up flags/runes. But the rest of my advice would be completely different
Kill as few weak troops as possible, keep the fodder alive! Strange advice you say? (They're not worth xp to us alive!)
Well yes but there are three important reasons.
Firstly they give piddly exp, secondly you may be unlucky to find a victory item later in the game (requires 50 victories before giving bonus runes) or alternately you may find the pain skull which requires you to go through 50 fights in a weakened state before evolving into one of the best items in the game, trust me you don't want to get to the end game only to find you have nothing to fight except hard fight and have to make it through the last areas penalised.
Last important reason is the pure cheese of the sacrifice spell, you can always return to earlier areas and use those weak monster battles to replenish your troops
Also I disagree with holding off the first boss battle, you want to take it as earlier as possible because the xp it gives is directly related to your level (same goes for all boss battles) There's a huge difference between the exp he gives if you are 5, 6 or 7. Level a bit with the quests, do the swamp quest (for access to Beholders and Royal snakes, very useful for taking down the boss) but I'd leave the cemetery and the other harder quests in the first areas (Frog quest,Spider bite quest,Castle assault etc) level to maybe 5 then take the boss on with +10% exp (+15 if you can afford it).
As soon as you've killed the boss go to the pirate islands and spend some time sailing around and picking up sweet leadership, do the pardon quest - the reward is a ring with +300 leadership...
and if you're a mage maybe do the inheritance quest to shop for good spells (the young brother has given me sacrifice before) and the ghost ship (he almost always carries a high tier spell (phantom or on a very good day firerain!) and some undead)
You can do all of this without fighting a single battle and little shinobi ninja dodging
If you're the planning kind you could push on, finish the islands and run through the dwarf lands for Lina and more spells
My mage hit the elven lands at level 11 (on normal) and no dryads
