You only receive 3 meelee points per level as compared to 5 for meelee classes. The gap only widens from there. It is doubtful that you will ever buy cloth armor as you will need all of your money to purchase spells at the lower levels. I generally only buy new robes and collect all of my armor off of monsters. Being a mage type class you have the fewest hit points in the game.
Wizards saving grace with all of their problems is the power of their spells.
However at early levels you will find that other classes can actually dish more power than you with their spells and can meelee better as well. This discourages many a young wizard and forces them to change to another class. Fear not however around level 20 the balance of power shifts and wizards begin to become one of the most powerful classes in the game. By far the most important ability score for a wizard is the intelligence attribute. Higher intelligence equals more mana.