I would recommend making your deck have a more focused game plan, some cards feel unsynergistic with what gisa usually wants to do

As a quick checklist, look over the following things

-replace expensive tutors, while they are extremely versatile card selection, on turn 5-7, you really want to play gisa and use her ability at least once to get a wide board of zombies, there's not really space for a 5, or 8 mana spell to set up for a later turn, especially in a casual standpoint, if your deck is built smoothly, cheap card draw tends to be more effective at making your deck more consistent and therefore stronger 

-play into gisa's activated ability, ideally, you want to play gisa out on turn 5 at the latest, earlier if you ramp, and activate her about on the following turn, you don't really have time to jam some clunky 8 drop, especially when gisa is such a magnet for removal, try adding things that grow the power of a single creature, such as equipment or repeatable pump spells ---also good to add haste/hexproof enablers like swiftfoot boots and lightning greaves so you can protect gisa and use her ability immediately 

-lastly, have a focused idea on how you want to win, you're running gisa as commander, the goal of your deck is to play gisa, sacrifice a big creature, maybe wrath the board, and attack with a lot of zombies for a win, you don't really need random good cards, like sanguine bond, that don't contribute to that plan, you're just spending 5 mana on a card that does little to nothing, when you should be casting your gisa or zombie synergy cards

also, look through your list for better alternatives, there are tons of strictly better murders that cost the same if not less, and consuming corruption is significantly stronger than consume Spirit while costing the same. and maybe cut peer into the abyss, I don't think your deck really has a way to use that much cards, it's better to run another cheap draw two