Welcome to Basenotes, Bianca!
I highly doubt that layering those two would smell similar to Portrait of a Lady. Besides, both are less wearable imo than Portrait. You need to enjoy the Montale-type oud to like Midnight Oud and appreciate linear, relatively dry woody scents to like 10CC. So I am afraid you would end up with no scents for the price of two.
I suggest that you buy a decant of Portrait then you can test it further. A sample is often not enough to decide it a scent is worth owning a bottle of. You could try to swap for a decant or check if somebody has one for sale on the wiki.
Alternatively, you could get the purse sprays (3x10 ml) of Portrait or the 50 ml bottle instead of the big 100 ml one. This way you would be spending less than for Midnight Oud and 10CC and you have the scent you love instead of poor replacements.
And hey, who says that you would have to wear it every day? You would only get bored of it.