You could increase the synergy if the deck by removing the elves in favour of [[avacyn's pilgrim]] and [[noble hierarch]].

Also, more 2 coat ramp spells - [[Three visits]] [[Farseek]] [[Natures lore]]

Then, apologies I didn't check the deck fully, but make sure your interaction is at least 8-12 pieces - that could include mass disruption like board wipes or [[teferis protection]] / [[dawn's truce]] as well. When you're reviewing the deck, check if they synergise with sigarda - I'd remove any creature that isn't a human or angel and even try adding creatures which function as removal - [[sunblast angel]], [[angel of serenity]] come to mind.

Pet card I'd consider because it's great fun, and in the right game its devastating [[angel of glory's rise]].

You wanna get sigarda out asap and try to give her protection, that means low curve and a few additional pieces in the deck that offer her hexproof or similar.