Best DIY module sellers from china

ds2313 rtc module for about 1-2 pounds.

it has an internal temperature compensated oscillator and keeps time dead on for years.
I've tried other modules that lose up to several seconds an hour.

other than that, cheap as arduino nano clones?

Gearbest is decent although they dont always have all the parts. Free shipping doesnt hurt.

For aliexpress, just go for listings with diamond rated sellers and check the negative reviews that aren't about not receiving the item (which is not indicative of the actual product, only the mail RNG they got or their impatience).
Never had an issue with a high rating seller. And always expect quality to be lower than listed (even if it's sometimes ends up being much higher than what you can locally at 10x the price).

Mind you it will most likely take over a month to arrive, so plan accordingly.

Thing to note is that a lot of those shops are actually the same source running multiple fronts. Fake competition to make everything look more legitimate or something.