Improve ping Gigacube?

Following problem:

We would get a maximum of 16K connection to the cable connection in our apartment. We had this right at the beginning and this was enough to play for 2 people, but we couldn't stream netflix via Wi-Fi with it. That's why we switched to the gigacube from Vodafone. We no longer have any problems with surfing and watching netflix, but online gaming is very modest, as the ping fluctuates extremely. Depending on the time of day, it is normal at 50ms to an unreasonable 500ms or higher.

I've tried to read into the whole thing, how to improve it, but can't find anything specific. It would be nice if someone can help me with experience reports or something similar. I'm thinking of installing an external antenna on the wall of the house, the only question is whether this actually contributes to improving the ping.

In the case of radio connections, due to the relatively low capacities, the connection is often only established when required. This is where it happens that you get such high scores. I'm afraid the best would be a hybrid solution, with a router that can be wired as well as wireless. Or go two ways. So netfllix over radio, gaming over cable. It's just a question of costs.