You could build a simple, but efficient, half-wave dipole antenna, or a sleeve dipole antenna. Examples: https://www.youtube.com/watch?v=KWLTKgrOTZM and https://www.youtube.com/watch?v=wcho1gJ2xEQ
NanoVNA can be used to measure the antennas (make the elements a bit bigger, and then cut them accurate according to NanoVNA measurements): Antenna improved range