Im not a big computer geek, and don't know much about computers so that's why i'm here. Im thinking about buying a server soon. So the question is, is 512MB of RAM good for 4 players? I'm also using this web host! http://apexminecrafthosting.com/Thanks guys!
Yep that's should works as each player for a good server will eat about 100mb a player on a plain minecraft server and for things like mods/plugins it depends on how much of a load you put on.
You can run Bukkit/Spigot just fine on 512MB. 128MB is enough for 2 players to play comfortably.