I find Oncidiums to be one of the easiest to grow. More so than Phals.
You don't have to be as stringent when it comes to watering like Phals and you don't have to worry about overwatering near as much as you would Catts.
Oncidiums do like bright, diffused light. More than what you would give a Phal.
Do read the culture sheet for Oncidiums if you do decide to get one. You can find the information here on the forum and on the AOS website.