Sometimes it's not necessary to buy certs - just depends what can be found online.
Griffith was born around 1880 and married as just Griffith - no middle name - so have a look at this 1881 entry - all children born  Llanystumdwy, Caernarvonshire which is the birthplace you posted from the 1911 entry
34 New St Ynyscynhaiarn
Evan Evans    30 b Harlech, Merionethshire slater and plasterer
Catherine  31 b Penmorfa, Caernarvonshire,
Lewis  7
Mary Jane  5
Evan  3
Griffith  1
John Roberts    17 lodger b Merionethshire - plasterer
RG11 Piece 5553 Folio 123 Page 40
Before going further forwards or backwards - it may be a good idea to buy a copy of Griffith's marriage cert to confirm his fathers name and occupation as there are 2 possibilities for his parents marriage