I will provide a run of RuneScape

[MMOruki]

I'm not a specialist on helms, however if you're slaying you want the complete slayer helm for RuneScape gold its own bonuses (similarly Salve amulet if it's applicable ) and Verac's helm otherwise. For boots, you will probably need to adhere to dragon. There are far better boots, known as"ragefire" I think, but I do not believe you want to devote your bank on them. For gloves, possibly barrows gloves from RFD or possibly goliath gloves in the dominion tower. Goliaths require you to have done plenty of quests and lots of arcade-style battle in a major tower filled with pursuit bosses. Something you could pick up when you have caught up in your questing generally, I think.

For your ring, there's a very pleasant free ring you get out of"A return to stone" (I believe that is what the quest is called). It starts in TzHaar city, in the pool. It's all of the fremmenik assault ring's bonuses, and a lot of rather nice reusable teleports, along with a combat bonus against the tzhaar. Or you might find the Berserker ring, that offers a power bonus, or you could get the explorer's ring, which delivers a few free alchemy spells each day, or you could get an Onyx ring and imbue it in mobilising armies.

Google that material if you want more detail. For your amulet, the fury (again, falling in price like bandos) remains generally thought of as the best choice. For your cape, you have the trimmed skillcape, or the fire cape, or the uber-fire cape which you get from giving up a fire cape and doing a minigame that's tougher than fight caves. It is tough. Very tough. You must do this quest for the ring I mentioned previously. It doesn't look great, but from what I have heard it's great stats.

Asking for your ability which makes the most money is extremely vague, so you're likely to have (and have gotten) some unrealistic answers. I will provide a run of a few abilities you may be interested in (in the manners in which they are trained by the majority, therefore it's the most realistic - except for Hunter - jadinkos don't make cash afaik but they are quite fast.

I gave reddish chinchompas as the profit making choice. Grenwalls are another option and more inclined to make money but they are a lot more immersion intensive and a lot slower exp/h - similar to runite's relation with Mining). Fishing out of 90-99 would create about 46M on Rocktails (I did not include the purchase price of living minerals, but I am making an assumption that will be negated by any profits made getting to buy RS gold 90 Fishing), carrying about 180-190 hours (again excluding levels before 90, and supposing ~42k exp/h).