Slayer isn't good charms, that's why. No new slayer monster he could unlock would improve the charm rate over camping the best monster until arguably 65. So finding the best monster is what he needs to do.
My friend is level 90, and is looking for a decent place to train melee and gather charms. Can you do armoured zombies at 70 attack, 60 strength, 70 defense and 52 prayer? Or is there a better place he should be training? Please do NOT suggest slayer. Thank you.
Steel Dragons Aquanites - bad xp, bad drops, bad charms, strong monster. Not really any reason to kill them. Hellhounds - bad xp, no drops, only gold charms. Iron Dragons unless you like them and have 85 herblore, really. Warped Terrorbirids if you have 85 herblore.
A good place to start is pineapples and willows and calquat, all rather cheap to plant. If you want more xp, upgrade to papaya and then palm, then consider upgrading to maples or yews.
Casting that many fire strikes would take hundreds of hours. You should use another method if you want to train magic. May I ask how you are making money right now?
For melee, the only efficient monsters to kill are undead monsters with prayer (Armoured Zombies, for instance) and either green dragons or spiritual mages. Anything else is just wasting your time.
My experience was that Kree only melees when no one is attacking her, so you would only need to run under when potting. This could be wrong though, as I have only soloed her twice.
preferably 2-3 kills per trip If you're planning to do this for money, then just focus on soloing one, so you only need gear for one. You'll have a hard time getting 3 kills at Bandos or Zamorak with your melee stats.
Don't bother with a cash pile over 100,000 coins, since moneymaking on the members' version is much faster than on the free version. EDIT: WOW am I surprised you found tip.it so soon, I didn't find it until I started the "Ernest the Chicken" quest.