There are basically three choices available to you and it’ll all come down to your preferred playing style and attitudes to risk.
For us, we really enjoyed using a melee build with Pyromancy (due to no need for any stats in Faith (FTH) or Intelligence (INT)) and a bow (and was the set-up you’ll see in all of our boss videos and screenshots). But it should be noted that players wanting to rain down magical-fires of death are very well catered for as there’s a large number of very capable spells/miracles/hexes available.
We recommend starting two brand new files and play up to the end of the Land of Giants boss with a pure melee and a pure magic class and then decide for yourself which one you enjoy the most. Playing with magic will make the game somewhat easier overall (more-so when using the really powerful spells later on); but ultimately base your decision on what you find the most enjoyable way to play.