I always have a jar of doubanjiang now - it gives such a deep savory spicy kick when cooking. I think some new world / pak'n'saves carry the Lee Kum Kee jar which i've used before and is ok but not quite as good as some of the other jars i've tried (I usually just pick one at random from my local grocer). At a pinch you could probably sub gochujang, its not the same but does a similar job. One thing I really like about this youtube channel (https://www.youtube.com/@ChineseCookingDemystified) is they try to show as authentic a recipe as possible but almost always include substitutions for things they guess aren't readily available in the west.

The other thing i've started having on stock are these packs of sichuan ma la hot-pot base. They're like a lump of chilli and spices and oil mixed together, i've used them as instant flavour for an otherwise fairly plain stir fry as well as a flavour hit to stews and braises. They have that spicy & numbing thing going on obviously so not everyone's cup of tea.