Creating A Universal Auction House?

alright so this one is quite the bit higher up than my alley but the system im trying to get set up here is like the World Of Warcraft auction house system but im not exactly sure how i would even go approaching this and i came here to see if its even possible or worth approaching because the only way i could think of doing this is getting scripts to pull from an external database which i have never dealt with besides making some free one only i found a couple years ago using PHP mySQL but im am not fluent at all with that or how i would get roblox to even pull from one but i think ive seen a game that does that but if there is a way could it please be explained as simply as possible i am only fluent in HTML,CSS,Javascript,Roblox Lua, and just starting Python but if this is not possible i can just make a Player-In-Server based auction house that i think would be a worlds lot simpler but mabye not because i think if there is a way to pull form the databasei can just make a script take those values and list them on a gui but also not sure how i could make Roblox send data back to the database