Players are constantly creating new armor, so if i were to say this is the strongest tomorrow could be something else, players are constantly upgraded and creating new pieces of armor.
Simple answer: you can't. His armor has not yet been made an item for players to use.
if you mean "cool" by the looks, then i would say rune (g) or zamorak for free players, and dragon armor for members. if you mean cool by stats, then rune for free players and bandos or barrows for members.
There are a number of suppliers but the one most players in the top regions use appears to that of the Rhino company
Members: granite armor Free players: rune armor
Go to your players inventory (on Xbox360 you hit y) and drag the armor into its correct slot next to your player.
The best armor for free-players is Rune, God armor is the same the same thing, just painted with the colors of a God. For members, the best armor is Dragon, also the most expensive.
amatteur baseball players
Yes
Usually baseball players depending on skills and how long the cantract is
Anywhere really. Armor drops from monsters, players can sometimes make shoulder armor, or you can often buy (horrible) armor in even small towns. The auction house has some but you'll want to stay away from that till you get a real feeling for the game.
There is no such thing as dragonwarrior armor on runescape. If you mean dragon plate armor, you need to have level 60 defense to be able to wear it. Dragon plate armor has good defense bonuses, but it is a little expensive. To get dragon plate armor you can but it at the grand exchange or buy ir from players. Some monsters on runescape drop dragon armor but it is usually a rare drop.