Even with prayer potions you'll probably gain from slayer, they are fairly cheap. From the drops you need to OSRS gold profit, and if you don't have that then buying Slayer Dart runes from the slayer master for 35 slayer points (you get 36 for performing 2 tasks from Kuradel) gets you about ~70k that is adequate and can add up to some decent money if you spend your money on this rather than cancelling or obstructing tasks.

I would recommend around 40 or even more atk, 40 or more str and 33 def or more before meleeing it. Maging it'll be awful like I read tht it's remarkable magic def. In the stated melee lvls, u wud need a rune scimmy (40atk needed), and complete determined armour (30 def needed), an amulet of str, and a str potion would help. . U also require the anti drag sheild, as without it, elvarg can hit upto 500 dmg.

Also, get a full inventory of lobsters/swordfish. Swordfish is a lot better, but I killed elvarg at around 40-50 combat, using just 3-5 lobbies. This installment is just for the final boss fight against elvarg the dragon btw. Yet another thing, having 33 magic can save u 10k gp (for telegrabing a map bit instead of purchasing it in the goblin). Also keep in mind, u need 33 pursuit points to even begin this quest. If u want to, don't hesitate to contact me in game (Tarun Dragon) and I would be more than happy to help u, and finance , if ur not good on money. The entire quest prices around 50k, to 60k. After I did it, rune scimmies at which 60k on its own, so that it cost me more.

Everyone has given you the best advice, except for two items. I believe that an amulet of electricity would be much better than strength, as it boosts you precision and defence. A short sword will beat a scimitar against dragons, that are weak to stab strikes. I wanted to mention that too, though I forgot he'd want the excess atk in his lvl, and yeah, dragons would be rlly weak to buy RS gold stab (was trying to think of an f2p stab wep, but cudn't lol).