Unfortunately WiFi boosters are becoming a bit obsolete. There are less and less open access points and the ones you do find have far too little bandwidth to be usable for things like Netflix. I would suggest you first take the time to bring a device closer to the access point and see if you have enough bandwidth to justify the investment. We generally stay at 8-15 different marinas/mooring fields in a given year and have not found one with enough bandwidth for streaming video in two years. Anchoring out you will general find nothing within range.
Another problem is many internet access points are cutting off high bandwidth programs like Netflix. Being liveaboards we do our laundry at laundry mats around our home port. I am now on my 3rd different laundry mat that blocks Netflix. Again the bandwidth problem is that if there are two people watching Netflix in the laundry mat then the rest of the people have the slowest internet ever.
If you do find you have good bandwidth at your marina and the issue is just getting a better signal, I would recommend you look into the
Rogue Wave. This antenna claims to have a 7 mile range. I think that is a bit of an exaggeration but I do know plenty of people that have made good connections from a couple of miles away. You can plug this directly into an Ethernet ready device or a WiFi router on your boat. But keep in mind that if you are on the hook or a ball that will likely need to be a 12volt device and there are only a few options and they are very pricey.
If you really want to go down this rabbit hole, read the
7 part article done by Jeff, the owner of
Active Captain. These are done by someone with a very high degree of technical knowledge and someone who lives aboard and makes his living from the internet.
Our experience is that the only decent answer is a good data plan. Since you can't get unlimited plans too easy any more, I would suggest you look into something like
Ting. Get a device that could be used as a hot spot for other devices. Watch the HD settings. We made a mistake one month and didn't have the HD turned off. We went through 30 GB of data in 3 days

And that was only day 10 of the billing month.
Good luck and fair winds,
Jesse