You'd need the kernel, the fstab and maybe some init.rc-scripts from the stock ROM (not the recovery). With that and some similar devices to your own as a "template" you could set up a twrp device tree. Don't use a "auto" twrp tool as they tend to be too straightforward to consider every aspect of your device especially the mediatek ones.Is there a way to pull configs and everything needed from a rooted device if you do not have source for said device? I have a twrp that is a little older but would like to update it if possible. I tried to manually patch it with mtk auto twrp, and while it seems to build it and it boots, I can not get it to actually mount anything no matter what I try. Would be neat to be able to build it.
As you seem to have a mediatek device the best thing to do is to find out your chipset (mine is mt6771 or Helios P60) and search for that on github. Chances are there is a quite similar device tree there you can use a guideline.
EDIT: The fstab and init.rc-scripts can be pulled from the running stock rom or from an official stock rom update file. The kernel itself can be obtained by some tools or also from an official stock rom update file.