Prestige is earned from building and upgrading buildings, researching, building defences, and training troops. The higher your rank, title, and level of your Town Hall reduces the amount of prestige you recieve.
Prestige goes up with every building built, every troop trained, every attack made, every technology learnt. so keep building/researching/training troops!
well i think your qustion is good because their are people over 200 mil i have seen them and i have one of them on my server so the most would be 200 300 mil and know one knows because there are so...