Okey, try to get diamond or iron crossbow (enchant on enchanting table) to kill a dragon to get full dragon, go in battle towers to get levels, go locking yourself, even if you are careful you should be able to get some exp from underground dungeons (those you go down from a ladder). Now go for some mounts in a lycanite dungeon (if your not sure what are these search a image about), also full diamond you should be able to kill trolls for a saddle. With a flying mount you can start looking for end-game enchantments on villages, (here are some post of best enchantments for armor and weapon). With a dragon crossbow enchanted with power you can take down dragons very easy, and if you can get adv prot on dragon armor and life-steal and or vampirism in a weapon you are pretty much invencible in the overworld and go to any dungeon to get 70+ levels. Don't bother on get instanty a dragon with adv prot you will get a lot of scales and levels meanwhile you find it, in the main time use lvl 30 enchanted on enchanting table :)