You are generaly looking for non chronos at 3 or 4 automatic movements
Asian 21j based on thre miyota, this can be a good movement and last for years and is generaly cheep to replace
ETA 2824/36 movements, very dependable and reliable but oftern surplus stock or older movements but can be new, to be on the safe side if it was keeper then i would get it serviced
Asian clones of the ETA movements above, some particuualy the seagul versions have a good reputation and on the whole i would be happy with these in Reps but they would generaly benifit from a service also, it has been known that people have orderd gen ETA but got clones so be carfull to get what you pay for.
Seagull auto movements, These are used in alot of panerai and Chopard with power reserve and other complications, these suffer fom a noisy rotor but apart fom that i have not heard of a lot of problems.
Chronos you are realy stuck with the A7750 which is no bad thing after a service there are generaly 3 versions to look out for with out other complications
The older A7750 with a fine regualtor that does not work, beating at 21600bph and the hand sizes as the swiss 7750
Newer A7750 beating at 28800 bph missing the fine regulator but wont take gen swiss hands with out modding the hands
Even newer A7750s with the fine regulator that still doesent work but looks better, same problem with the hands
All are good movements but require a service but there are limited people that will work on these. New movements can be bought from cousins UK for less than