Hi Ernie.
I've travelled from Stoke to this area a few times with a van and as you are probably aware, there are a few choices of route.
For me, the one I usually take is the A500 to Nantwich, then A51/A524 to Wrexham. Pick up the by-pass to join the A483 towards Oswestry then the A5 through Llangollen to Corwen. After Corwen, turn left onto the A494 to Bala. Once in Bala, turn right onto A4212. This road takes you round the Llyn Celyn reservoir and through some stunning Snowdonia scenery.
The road meets the A470 where you would turn right towards Porthmadog. Incidentally, the CC site Coed-Y-Llwyn is a couple of miles down the A470. Once in Porthmadog, pick up the A497 to Pwllheli and then A499 to Abersoch.
From Stafford, you could also travel to Eccleshall/Market Drayton/Whitchurch then via either Ellesmere or Overeton to pick up the A483 at Wrexham. Another easy route is the A55 coast road and drop down to Porthmadog via Caernarvon.
The closest site to Abersoch that I have stayed on is Eisteddfa Caravan Site in Criccieth. A very nice site with good facilities and sea views.
Hope this helps you.