[RPG] Can creatures without hands (and as a consequence fingers) use rings

Well first off, to answer your question about magic item limits, a character in 3.5e is limited to two magic rings. Found here: http://www.d20srd.org/srd/magicItems/rings.htm in the very first paragraph.

Second, AC bonuses do not stack unless they are different types of bonuses (armor, deflection, shield, etc.) or state that they stack. Usually, you cannot stack bonuses of the same type. Found here: http://www.d20srd.org/srd/theBasics.htm

Third, to limit the buying of any item you could always add a bit of realism and force them to buy items at shops. Shops do not have unlimited supplies, therefore limiting the amount of any certain item they have. You are also not obligated to have the shop selling the item for what the book says is "list price."

Fourth. sit down and talk with your players about your concerns. Express how you wish to place limits without looking like the bad guy.

No you can't, but not for the reason very often stated, that "you can't stack bonuses from the same magical source", which isn't stated as RAW anywhere that I know of.

The actual reason is the following rule:

Attunement (DMG p.137)

Additionally, a creature can't attune to more than one copy of an item. For example, a creature can't attune to more than one ring of protection at a time.

So you cannot attune to more than one copy of an item, with the specific example given of two rings of protection. You only get the benefit(s) from the one you are attuned to.

This means if you have two of the same item (whatever their bonus is) and they require attunement, then you can only attune to one of them and therefore only get one of their benefits.

The incorrect statement often used as to why you can't benefit from two rings of protection (for instance) appears to comes from the assumption that the combining magic effects rule applies, but this is for spells only.

Combining Magical Effects (PHB p.206)

The effects of the same spell cast multiple times don't combine, however. Instead, the most potent effect—such as the highest bonus—from those castings applies while their durations overlap.

The belief is perhaps also a holdover from previous versions of D&D which had rules about how many rings you can wear and the combination of magical items.

DMs should be aware and careful of this, as if items that do not require attunement (for example special rings of protection) are given out to PCs, then there is no RAW that says that their bonuses do not stack if two were worn by the same creature. I've looked through the magic items in the DMG and it looks as if the designers have been very careful in this regard to ensure that you can't get stacked bonuses in this way due to what must be attuned to.