Chaeldar requires 70 or even 80 combat (i don't recall) in addition to access Zanaris. Black Mask can be easily purchased from GE for just a few hundred dollars. It's necessary to OSRS Gold For Sale make a Full Slayer Helm anyway so don't think its an unnecessary expense. You can buy the uncharged models. I'm not a slayer who prays during the slayer since I'm not an efficient slayer, but perhaps others might know more.
Since ur f2p, u cannot range elvarg, the dragon, since the single-handed rng is the weakest crossbow you can use in game. I'd suggest 40 % or greater atk, 40 or more str and 33 def or more before throwing it..
Rnging it will get u killed as you are not able to wield an anti-drag sheild (unless you're using bronze bolts when using a standard crossbow) that's something i would not recommend. Maging it will be awful given that I read that it has amazing magic that is definitely. In the melee levels it will require a rune scimmy (40atk required) as well as full Adamant Armour (30 def required) as well as an amulet made of str and a str potion would help. Also, you need the anti drag shield, as without it, elvarg could be able to hit up to 500 dmg.
Also, get a full list of lobsters or swordfish. Swordfish is much better than lobsters, however I killed Elvarg with around 40-50 fights and only 3 the lobbies. This is just to get you ready for the final boss battle against the dragon, elvarg. Another benefit is that the 33 magic spell can be a huge help in saving 10k Gp for using telegrabbers to grab a map instead of buying it from the goblin.
Also , keep in mind that you'll need 33 quest points to begin this quest. (u must complete nearly all the non mem quests in order to earn the 33 points) If u want to RS 2007 Accounts you can contact me in game (Tarun Dragon) and i'd be more than willing to assist with u and pay for u when you're struggling on cash. The entire quest is priced at 50k, to 60k. It was the first time I attempted it. the rune scimmies cost me at 60k and it was significantly more.