If you want to make a low magic world then this might interest you. The exact opposite. The world of Forgotten realms in times of giant empire of Netheril (which is my favourite btw.)
Back then everyone knew magic. Literaly. For example a barmaid might know a spell to keep her from falling over. Or to serve faster. Archmages ruled the land. They went as far as to challenge the gods themselves, with an unfortunate accident of casting "Karus'es avatar". This powerfull spell
STOLE THE POWER OF A GOD AND GAVE IT TO THE CASTER!. Things went wild from there when Karsus stole the power from Mystra, the godess of magic. She sacrificed herself to prevent a catastrophe of larger proportions than destroying the magic of the whole world (so... yeah). Of course the big bad wizard got his karmic death. Magic went WILD. Every spell was dangerous. Common people lost their ability to cast spells. The spells effects were totally random.
Things that might especially interest you, and be usefull:
The permanency spell. Magic items didn't work back then like they do now. Casting such a spell to prevent the enchancment from dissapearing took a point of constitution from a mage. This can have fatal consequences on a life span. Sort of like smoking I guess. Just do one or two and you lose about 5 years of your life. That's why true magic items were so rare back then.
Semi-magic item. Are magic items that have no power without a magical power source nearby. In short the're useless normal items, but go into a magic field and they kick yo ass! They were so popular because, there were flying cities that used such power sources, so inside a city every such item worked. True magical items were only needed "out in the field", as wilderness was dangerous. They didn't need a mage to sacrifice his life force to make them... so, yeah.
After "Karsus'es Avatar" killing mystra, her reincarnation changed the rules of magic completely. Normal people lost their power, and no mage was ever allowed to cast a spell bigger than 10th level (Karsu'es avatar was the only 13th level spell ever made). Gods are paranoid about powerfull spellcasters. And get this. Every spell has to be learned from a scroll when you're talking about a wizard. Your world is purely islands? This pretty much prevents wizards from ever having more than 10 spells at a time. So don't worry about them. You have an environmetal explanation why there aren't many of them. Also they need huge libraries to make new spells. Whithout ability to collect such books in such a dangerous world there won't be many new spells ever made. Sorcerers and Clerics far more powerfull than self-learned wizards. Sorcerers require celstial, demonic, draconic or otherwise magical blood to even exist, and clerics need to be granted power by their god. Let's say that no magical race really likes human, so not many sorcerers born. Let's say not even the gods like humans. Not many clerics over there.
If you combine such characteristics into your world you get:
a) a good reason why magical items are so rare.
b)a good explanation why there aren't many casters.
c) You don't take any parts of the game away since powerfull magic
still exists, it's just so rare. Even the very common magic.
DARN IT! I wish I made it into the game. I had such a cool half-orc-one-quarter-human-one-quarter-dwarf-alcoholic-barbarian. *Sob*
. Goodbye Gurk, I'll never play you again.