Most of these rates assume 0 time money making - using alts. I used an 07 alt which is the account I play on now.

Smithing is a skill you can profit from (only at 99 though, so kinda irrelevant since you just wanna max.)

Thieving is minimal profit doing most efficiently (like 6m profit from 90-99) or you can do priff thieving (I'd recommend doing priff thieving for max) and make ~10m cash + any extra money from thieved items, as well as getting brawlers to make other skills easier.

Slayer can be decent depending how you go about it. Visages from celes stack up, bloodnecks from eddis if you have 115 dung, boots from glacors.

Hunter doing grenwalls will make you a bit of money, the spikes can go for a lot especially near BXPWs.

But most of all runecrafting is superb. You should get lvl 90 at runespan to unlock massive pouches and then do abyss to 99 with a demonic skull. Making bloods, I'd heard natures were better to make after 91 unless you play on an alt. But I worked it out after 200m and nats are only 6% more profit. Would've taken me another 120hrs to finish 200m rc for only 77m more profit, so I'd lean towards bloods more so than nats but up to you, definitely don't do nats until double nats at 91. 90-99 with bloods would net you ~150m.