What is the lowest useable load for 22-250 Rem and can anyone point me in the right direction to find loading information for this calibre?

The first thing to do would be to get a reloading manual. I believe the manual that has the best overall information on reloading for a beginner is Modern Reloading by Richard Lee but I don't particularly like the format for the load data. For load data, I prefer the Hornady, Speer and Barnes manuals in about that order. Hodgdon's load information is available online at:

http://www.hodgdon.com/index.php

Seafire, who posts on this forum has worked up a number of Blue Dot loads for various rifle cartridges. If by "lowest usable" you mean low velocity and recoil, he might have the information you're looking for.

Thanks for the "heads up" on this one. Much appreciated.