TP-Link Archer MR200: Any advice to change the 3G/4G external antennas to get better signal?

I have a TP-Link Archer MR200 upgraded to the last version of openwrt working like a charm.
The problem is that I live in the country and with the default external 3G/4G antennas doesn't get enough signal to connect to the mobile network.
Any advice to replace the external antennas (rp sma connector) with a better gain ones?
I have seen several antennas on aliexpress but I would like to hear any advice before to buy one of theese:!EUR!5.61!5.61!!!5.87!!%40211b88ef16939892593283435e3298!10000015659061977!sea!ES!2352207606!&curPageLogUid=tiiLn17raL9e

Unrelated to OpenWrt.
First you need to determine the best/closest base station location, what bands and bandwidths are available there, etc. Having this information ready you can ask questions in specialised forum(s).