PCB design consideration for a SMA antenna
You need to learn about fixed impedance traces.  A good resource for calculating the trace width for impedance is Saturn PCB Toolkit

Most SMA connectors have pins for surrounding the signal with ground plane, or SMT versions have recommended via surrounds.  The idea is to surround the signal in ground, just as the outer braid does in a coaxial cable.

FR4 PCB material should be fine with the frequencies you are talking about.  Designs are working on FR4 with no issues quite a bit above 1 GHz.

The important thing about not generating reflected signals is reducing impedance mismatches as much as possible.