On my first time on percodan (which is pretty much the same thing as what you have) I had 2 45 Mg pills.
I split one in half, mashed the half up and snorted it.
Didn't do much to me.
Next night, I snorted the other half and a half of the other pill.
It actually worked for me that night.
I got really bad stomach aches for that night and the next morning but it was a fun high.
I felt like a little kid again.
A little kid with a burning stomach.
I recommend that you eat alot before you take the pills (if you don't, you'll feel the way I did).
I also recommend snorting, in case the pills are time released.
So, I basically recommend 45mg's for your first time.