What type of backend to use for iOS app

I've created an app for iOS using Swift that is essentially a Latin dictionary. Users have the ability to create new words that aren't included in the app. The data is stored locally in the app's document directory in two SQLite databases. The first one holds the words that ship with the app. The second holds the words that are created by the user.

I want to have each word created by the user uploaded to a server at runtime and added to a master database of words. That server would then compare each incoming entry to William Whitaker's Words to see if it is in fact a valid Latin word and then to see if it is already in the master database. If it is valid and not already in the master DB, then the word would be added. After every new entry to the master database, the server would generate a new SQLite database that includes the new word. Every time the app runs it will check for a newer version of the StandardData.sqlite file and if there is one, it is downloaded. Words that are common to the Standard library and the user's custom library would then be deleted from the custom library to prevent duplicates.

Over time a large library of Latin words would be created without me having to manually enter them in from a dictionary.

I'm somewhat familiar with MySQL (When using it with MySQL workbench) but beyond that I'm mostly unfamiliar with today's web programming tools: HTML5, CSS, JavaScript, Java, Ruby, Rails, PHP, etc. My budget is 0$ and ideally I would like to host the server on my own hardware. What is the best way to add a backend to my app?