Birth certificate/Evan Evans

[erylthepres]

I am having difficulty in obtaining birth cert for my gt grandfather born circa 1840.
His parents John and Elizabeth Evans (nee ?).
The census record from 1851 shows born at Llanddwywe, his mother at Llanenddwyn and his father at Llanfihangel. He had a brother John c 1838.
1861 C shows born at Llandecwyn.
1871 C shows born at Llanenddwyn
1881 C shows born at Maentwrog
 
Evan Evans has  a few entries on Ancestry but causing  a dilema on choosing the right one, not even sure what district to look in.
Sorry for being long winded, can anyone help at all?
Thank you   Eryl