In reply to Hubert1982:
In 2-3 days, you could trek from Barmouth to Penrhyndeudraeth. I did this route summer 2013 in 1.5 days:
https://osmaps.ordnancesurvey.co.uk/route/2156828/Rhinogs
1.5 days was far too fast for me with a heavy pack, it was tough, but 2-3 days should be fine. I camped at Diffwys, and on another occasion I have camped at Llyn Hywel just below Rhinog Fach. Both were lovely spots.
My route up Moel Ysgyfarnogod following the dry stone wall was not good, and I would suggest researching alternative paths up.
The Rhinogs are one of my favourite areas in Snowdonia. They're much quieter than the big peaks further to the North.
If you have a car, then you could leave it at Barmouth and get the train back to it from Penrhyndeudraeth. The line is one of the old fashioned ones that survived the Beeching Axe, so every few minutes it stops in a coastal hamlet. Very quaint.
**edited for typos**
Post edited at 11:42