Best way to strengthen public wifi signals

I’ve been in a van for a few months and loving it with the ups and downs as always. Right now I’m using my phone as my main internet source The hotspot is good enough for me. I’m considering getting a booster to increase the strength when I’m in more remote areas but I’m also considering rigging something up to increase my ability to get wifi from public places like coffee shops.

The issue is I really have no idea where to begin. Have any of you found a system that works to increase the strength of public wifi. Ideally it would be nice to sit outside a coffee shop and work in my van while using their wifi to download stuff or stream stuff.

My unlimited data is great and I’m just about able to make it through the month but near the end I start maxing out my plan.

Anyone with suggestions to create something that will work?