🙋🏽♂️Heya Aergia1,
While there are a significant amount of West Indies (and Trinbagonians) who play League, I don't think we're vast enough to warrant a server of our own. You'd have to take into consideration queue times and queue health (are you being matched with/against players of your MMR or are you being matched with players of divergent MMRs to your own).
This would be the main reason why Riot probably won't open a Caribbean server. The South American server is one of the lower population servers located in bigger region than the Caribbean, you can fill in the blanks.
As for pings Digicel is currently the best ISP in the country with regards to speed, quality and service. Forget Flow, Bmobile and Greendot, they're inferior.
Your ping is highly reliant on your upload speed, the higher your upload speed, the lower your ping would be. Selecting a package with higher upload speeds would reduce your ping. Take a look at the packages and pick the best option for your budget.
Also, you might wanna try Riot's Lag Report. It'll let you know the quality of your connection and provide some tips where appropriate.