Can you see your provider’s base station tower from your rooftop?
Depending on where you are, how tall can you install the antenna in your house/building, and if there is a unobstructed Line Of Sight (LOS) from that point to your provider’s Base Station/Tower/Antenna, you might benefit from a directional antenna. If so, if you have LOS, a directional antenna might be the best choice for you. If not, then most probably, an Omni-directional antenna (or antennas) might be better.
Be sure that the Provider’s Base Station you’re considering, is the one from your provider, meaning, from the same company from which you got the SIM card for your router.