The only reading you haven't learned for this name is the irregular わら reading for 原, so here's a mnemonic to help you:
Sugawara-san went to war a (わら) long time ago, but these days he enjoys a quiet life tending to his sedge fields.
Sugahara's a cool surname, isn't it?
Oh, Sugawara-san, do you have a cold?
At Sugawara Shoe Store, I bought a pair of stylish leather shoes.