Do not attempt to be somebody else, or OSRS gold emulate other people's stats. Runescape is a open game that never ends, unlike quests. In Dragon Slayer, if you conquer Elvarg, you acquire the ability to wear a rune platebody or a green dragonhide body. It's not like that would be the end of Runescape, along with your Runescape reward being a Santa Hat. There is no reward in any way, and definitely not a Santa Hat.
Magic: Now you when you have enough cash (~40k) buy a water team, couple hundred ground runes and few hundred body runes. Now throw contested until level 11, subsequently weaken to level 19. As you may cast these while safe-spotting you won't need food. If you run out of runes or get bored you can always return to other abilities, get money and come back later. You can even throw battle spells if you want to.
Right, subsequently throw curse to level 25, Varrock teleport to level 37, Falador teleport to level 43. Since you'll need atleast 15 Smithing to make iron bars(or even 30 for steel bars; both are very good, depends on personal preference) I would say train your Smithing (and Mining while you're at it) There's also a inexpensive way to level up magic. Do Imp Catcher quest and Witch's Potion mini-quest. Gets your mage up to level 9. Get your defense up just a bit, then buy from the Grand Exchange: team of RuneScape gold buy atmosphere, wizard hat (blue or black, it does not matter), wizard top (again either black or blue ), amulet of magic, leather chaps/gloves (for defense).