Well if you have 45 def, I would say go for Rune armors, chain or plate depending on if you have completed Dragonslayer or not (or paid 1m perm fee to wear rune plate without quest). I would recommend taking both attack and defense up to 60 for now and str 80-85.

Attack 51? I'd recommend get it up to 60, get yourself a dragon sword and complete Lost City quest (gives you access to wear Dragon sword and is very fast and quite easy to complete)
Before that you could use Rune battle axe + Rune kite for extra armor & less food loss in training or just go for Rune 2h and without shield. Either one works.

Conclusion:
Rune full with Rune Chain or Plate depending on your quest status
Rune 2h / Rune battle axe or Dragon long depending on your quest status and once you have attack 60
Ruby, diamond or dragonstone amulet as amulet
Any color cape
Any color boots / gloves

What about for me? I have 50 Attack and 60 Strength and 60 Defense. I don't have the quests done or GP yet for Dragon Armour though.

New pkers building:

Mith, addy, rune armor.
Confuse, weaken, curse. Runes and wiz top.
1 body, 3 water?, 2 earth? Ect.
Str or diamond or magic or accurcy depending on stats.
30-60@ttack, 1-60 d3f, 60-99 str, 70-99hits
14-66 magic or 99
31-99 prayer
99 fire make or 99 cook or any EZ 99 for p2p200k pk capes

All newbs wear these capes,

Red,black,blue,any color 2 def
Hunters cape, 2 def (valueless cape) pking gear now.

Pros use purples 2def, hunters 2def, or 99 caopes p2p

Ill drop all gear u need to add to 3 item training pkkers. Pickup free pk or training gear in wild.