For this deck I would encourage the use of
setessan battle priest and the white jeskai creatures that also have first strike and life link effects. This way whether your opponent takes the offense against you, you'd still be able to defend yourself and STILL gain health. Also playing instances that give you first strike and enchantments such as
divine favor, creatures like
auramancer and
arashin cleric would be good ways to gain health and keep good field presence. Having life gain be the theme is not a bad strategy, but you are going to need a strategy as far as game plans go. The trick to a good life gain deck that is also mono white is being able to create synergy between the creatures and spells you play. for example, if you swung with
setessan battle priest and then played
feat of resistance she would gain +1/+1, protection from any color, you'd gain 2 life AND she would survive combat while destroying the other person's creature. It's the little strategies like that which help make decks last for the long haul.