I don't think the order in which you book really matters tbh. Just try to make sure everything is refundable/able to be changed. The flight and the ASQ. I was just like you and found the whole process a nightmare. The visa was the worst bit as I had to upload 12 documents. The Thai Pass was ok as I'm unvaxxed so they didn't have to check vaccination certificates etc. and the pass came through right away. Print everything out. You can do it! I so know that feeling though..x