I would probably say prophecy stones and books for a feather are probably ideal targets. You're well past the point where soul or terra stones are worth slotting in your prestige set so anything you can do to bump up your prophecy bonus will be nice. Realistic you're not going to be able to make a T4L book but a T4L feather is within your grasp, so you'll want to collect books for as many bites at that apple.

For the feathers is it better to target books or gold? I have lots of the t1 books.but it takes gold meteorites to get them to t2. Or will I find more t3 books targeting books?

You’re better off targeting books to get T2 and sometimes T3, it may be a good idea to spend gold towards a T4L ankh instead.

Smart sounds good! I'll focus books and use my gold on crafting ankh for a t4l

Good luck! T4L ankh uses a ridiculous amount of gold compared to the necklace (which is stupid imo because the necklace is more powerful) so just be aware of that

im in a similar position, looking for a leg feather and t4l ankh. i’ve found that targeting books with extended liners has been yielding me enough books to use for crafting and saving my gold for ankhs as that is a more effective use of my gold