Where are you mounting the antenna?
I have one unit that has to stay indoors and unobtrusive on a window sill, and have been impressed by the difference this antenna made for less than $12.
Superbat 900MHz 3G 4G Antenna 9Dbi External Omni Rubber Duck Antenna with RP-SMA Connector + RP-SMA Female to SMA Male Adapter for Cell Phone Signal Booster Router Security Camera Gateway etc. https://www.amazon.com/dp/B07PZFV9NK/ref=cm_sw_r_cp_api_glt_fabc_R4286VB2W9S3ATT57QHQ?_encoding=UTF8&psc=1
I saw the 9dbi on Amazon for $9 here
Sure it's this one https://www.amazon.com/gp/product/B07PZFV9NK/