Food :
If you roll a lot to evade attacks , so stamina consuming : serpent stew , eyescream and onion soup
If you wants some more hp : serpent stew , wolf skever and eyescream

Get full silver gear and use obsidian/needle arrows or poison arrows
If you try meele ( i dont ) maybe silver shield and iron mace or more risky fang spear, silver type weapons are not effective vs that dragon , only the bow

Rested buff at full lvl , tasty me/asd for stam regenerations and health and stamina potions