Out door aerial is your best bet but it will cost you
Depending on your location to the nearest internet provider wireless station will really help answer your question
Your first step is to ring you ISP and ask them how far away from it you are and what they recommend
There are directional Antennas. Omni directional etc all are typically inherent to LOS (line of sight) issues unless they are using microwave ie 3g or 4g which will make an impact on type of aerial needed for best reception.
Are you portable or fixed in location... a simple 9db gain may go the trick but then you may need something stronger