I don't think there is any such thing as a player-owned shop in RuneScape.
the genral shop
You can buy them at Best Buy or Future Shop.
varock ranging shop
Buy it in Falador in the Alchohol Shop.
You can buy watering cans at farming shop's or the grand exchange (have to be member)
You can buy one at Port Sarim Fishing Shop.
You can make the at the water altar, buy them from a rune shop, or buy them from the Grand Exchange.
You can buy one from the Grand Exchange or you can buy an Addy Square shield from the shield shop in Falador
None that I know of, but buy rubies at the gem shop in falador.
You can't make charcoal in Runescape, however you can buy a piece of it at a shop in Karambja, just past Brimhaven. ( Members Only )
You can buy one from the grand exchange or their are some hatchet shops around runescape.
U can either buy a maple long bow from the Grand Exchange or there is a bow shop in Verrock.