Your current issue is that you depend on a lot of things going right and on a slow win condition in a fast format. To turn on
Gate to the Afterlife faster, some cards like
Thought Scour may prove useful, and is also a cantrip. Any way you can dump cards into your own grave fast enough, if you want to have a chance of winning.
You also seem to be a bit too all-in on the infect plan. Some basic utility like
Fatal Push and
Remand (Or alternatives if you're planning to play on a budget) would be helpful and up interaction, so your opponent can't just do their thing and suddenly win, like
Ad Nauseam or
Scapeshift. Also, basic sideboard tech might also prove useful for you.