Email or telephone exchanges with me will save a lot of time and trouble. Don't hesitate to call me or send me a quick note via email. Going to my order form and filling in all the details that make sense to you would give us a starting point, and does not commit you to anything at all. I wouldn't accept payment until I know what's being ordered, anyway. I have rings, bracelets, and earrings that I make to order.
Pendants are just larger earrings, generally, even when they're wrapped around a stone of some sort.
Chains are made with a series of knots, and are seriously labor intensive, time consuming, and commensurately expensive. Earrings and pendants are not size dependant, although I can accommodate varying tastes in that department. The third situation where there is a need to be precise as to size is if you want me to make a knotted bezel for a stone, but that would be a minor consideration among the other complications of such a project. If you do not know your ring size, there are ways to overcome that difficulty. Call me or email me for details.