Kill green/blue dragons or do something else that is easy, quick money.
Then you buy some basic combat equipment like full torag and a whip, even if you have the funds you can get 70 prayer and an amulet of fury as well.
After this, you train slayer to also level your combat stats, starting with 70 def -> 80 strength -> 80 attack, when you are done with this, you take a break from slayer to do some dungeoneering, and get yourself a chaotic rapier.
When you have acquired this, you keep on slayer until you are 99 in all the combat stats, and you should end up with around 97-98 slayer. This will also give you the charms needed for 96 or even 99 summoning, which you will want to help you with bossing.
From slayer you should also have a bit of money to level your herblore and slayer a bit, and even if you can't reach 95 prayer/92-96 herblore it should still get you a fair bit on the way.
Now, you have an account with maxed combat stats, hopefully 96 summoning and atleast 70 prayer.
With this, start bossing or kill frost dragons to make bank, go with bandos/frosts first until you can afford 95 prayer and 96 herblore if you couldn't with be money you made from slayer earlier.
You can also do some more dungeoneering for a chaotic maul if you wanna kill bandos, and even a chaotic crossbow, eagle eye kiteshield and the rigour prayer if you wanna kill nex or arma later on.
Good luck.