Glissa was one of the first decks that made starting out with MTG and its evolved a lot over the years. It started out a lot like yours without the inclusion of the Necrons. I'm going to tell you a few things that I've learned and link my current deck down below.
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You're going to end the game with an overwhelming board or just lots of small attacks. Glissa has first strike and deathtouch, no one is going to want to block her. Anything else that dies should hopefully just come back with her ability.
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Don't over worry about self milling. It's a good way of getting more options into graveyard, but usually you just want to replay something you already had on board and sent there for more value. And if someone has a Bajuka Bog or other graveyard hate, then you're just losing cards.
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Make sure your deck can still do things without Glissa in play. Unless you have multiple ways of protecting her, having a commander be one of the main engine pieces to your deck makes Glissa a big target for removal.
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If your opponents don't have creatures, you can't combo off Glissa. I seen that you have other recursion in the deck which is great, but it's something to keep in mind.
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Cost reduction over mana dorks. I ran every mana myr possible starting out, but ended up cutting them for cost reducers since you have a good amount of them for artifacts. They add more value over the course of a game.
I think your deck is great for what it sets out to do and that it will be a ton of fun to run. You're just probably going to have to end by a mixture of life loss cards and combat damage.
This is my deck if you want to take a peek. It's far more combo heavy and leans into what typically would be one time use artifacts and mana reduction.
https://www.archidekt.com/decks/1133762#Glissa,_Artifact_Necromancer
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