Nasus is extremely easy and, at early levels even, is one of if not the best 1 vs 2 laner. (You don't really need runes even) Get one rank in Q for last hits. You need to farm with this by getting last hits asap so you can do insane damage with it later in the game. Then, concentrate on maxing out E. Once you hit rank 2 and beyond with e, it's really easy to keep creep waves off your tower and farm at the same time. Just use it on a creep wave, which will cause the other 2 champions to back off, and run up to last hit/farm your Q.
Without runes though, I'd recommend maybe starting with a meki pendant for the mana, and maybe even building that to a chailce of harmony later.