I know that if I have a weapon I can enchant it from a +1 to a +2. I also know that I can enhance a "Ring of Protection" from +1 to a +2.
My question though is if I have a "Ring of Protection" can I add the affects of a "Ring of Sustenance" to it or do I have to create it that way all at once? I know that I will have to pay 1.5 on the cheaper item.
Furthermore if I combine a "Ring of Protection (+1)" and a 'Ring of Sustenance" I have to pay 5.5K( 2500 for the "Ring of Sustenance" and 3000 for the "Ring of Protection (+1)" (2000*1.5 to combine the items). When I decide to increase my "Ring of Protection (+1)" into a +2 I have to pay 6K to increase it. Since the cheaper item is now a "Ring of Sustenance" would I have to pay an extra 250 gp to make up the difference between the extra cost of a ring of protection and a "Ring of Sustenance"?
It is simpler if you use the difference in total costs instead.
You have a ring of sustenance and resistance(+1). It costs 5.500 gp.
You want a ring of sustenance and resistance(+2). It costs 11.750 gp (8.000 + 1½*2500).
To make it, you need to the difference: 6250 gp.
In other words, yes you are correct:)
And just how many magical effects can be stacked onto a single magic item before it starts to glitch, fail, or explode in your face?
Since items with multiple enchantments are custom items (with the exception of the examples listed in the book), and, as such, subject to GM's approval...
As many as you can afford. Or as many as your GM allows. Whichever lower.
Cool thank-you very much for the help.