Minecraft plugins program bronze only visible and collectable for certain players?

Minecraft plugins program bronze only visible and collectable for certain players? How does it work? This is for a special BedWars system!

You have to do this with packets, look on youtube or in forums by spigot or bukkit then

Thanks vlt. I think something

Collectible for certain players is easy
but that "only visible to certain players" becomes very difficult with packages