‘Magic Shops’ are rare!  They are found ONLY in cities with large populations (at least 15,000) and unless the city population exceeds 25,000 or there is a magic school present, there will be only one shop in the city. 
Most Magic Shops only sell basic material components and the common ‘tools of the trade.’  Blank spell books, scroll making supplies, flasks for potions, etc.  You can also find, (in some shops,) finely crafted wands, rods and staves that are suitable for enchantment.  Materials and ingredients for SOME potions, and Fine Grade weapons (usually only daggers) suitable for enchantment.
VERY RARELY, perhaps 1 shop in 10, will have very minor magic items for sale.  (DM will provide info as needed.)

Material Components


At 1st level it is assumed you start with all the components needed to cast the spells you know at least a dozen times.  (12 grasshopper legs, etc…)  At some point the character will need to spend some money to restock.  The cost of Material Components is lumped together as 5gp per Level of the HIGHEST level spell the Magic User can cast.  So a 5th level mage, who can cast 3rd level spells, will spend 15gp (5 x 3) to replenish ALL of his/her material components (except the weird/expensive etc.)  For convenience assume that the supply is sufficient for a month of steady, daily, spell casting at which point the mage must resupply.  (So for a sea voyage or wilderness excursion that may last several months, the MU must stock up.)
Examples of Unusual or expensive items.  Pearls, gem stones, monster parts, pieces of Saints, etc.  These things (and others as determined) WILL require role play!

Most shops know the magic users in the area and also have contacts in the Magical Trade.  If PCs are seeking a spell to be cast or to sell or trade an Item, the shop keeper will get in touch with his contacts and pass on the word.  He/she will NEVER give the PCs names, addresses etc.  They will only pass along the PC’s request. 

Typical Inventory

* See description of Elvin Healing substances