If you're looking to spend very little (under 10M) Then a set of Barrows armour and some nice peripheries (fury, though that's not necessarily the RS gold most effective) still gives fantastic bang for your money. There are, however, a few very nice things to consider. I'm assuming you haven't been here long.

The rapier is a bit erratic. Very powerful one-handed melee weapon that you acquire after a period of dungeoneering: you need at least 80 dunge to get it, making use of the dunge reward system. Most chaotic weapons are the most powerful of their kind.

Bandos chestplate and Tassets. Prices are dropping, but these are usually the top choices If you're in the market for cash. 12M for one item or buy OSRS gold 12M for another. They also give boost in strength and a prayer bonus.