I realize this is an old thread, but I would start with this excellent pdf for the conceptual aspects:
Getting Started with Oracle Spatial by Tim Armitage
Then move onto the dev guide (11gR2 here, about 900 pages worth):
Oracle® Spatial Developer's Guide 11g Release 2 (11.2)
At that point you'll be informed enough to integrate Oracle Spatial professionally into any Desktop GIS application. Specifically for ArcGIS, here's the ground rules and documentation for using SDO_Geometry within ArcSDE geodatabases:
How do geodatabases use Oracle Spatial?