I would say a low level rune pure. 40 attack. Around 60 strength. 40 defence. 70 range. 25 prayer, for protect item (rune can get expensive) You'd be around 63 combat with these stats, hitting pretty decently and you would be fighting one defence pures most of the time, so you'd hit a lot better than usual. Mage doesn't really matter, because it's generally ineffective in f2p, and considering you'll have 40 defence you should be wearing rune armour, which makes maging even more ineffective. If you do chose this type of pure, you should do dragon slayer at 34 defence, so when you complete it the defence experience you get from the reward would bring you to exactly 40 defence, allowing you to wear a rune platebody and green d'hide body. While pking, I suggest ranging with a rune full, green d'hide body, rune legs, power amulet, adamant arrows, green d'hide vambraces, fighting boots (from the stronghold of security) and a team cape; for a decent defence/range bonus. Also, bring a rune 2h or rune battleaxe with you, and when they're low hp from you ranging them switch to your rune weapon and try to KO them. Hope this helped, if you have any further questions feel free to ask, I'll do my best to answer them. Gl.