Well I think I will share this to get the F2P investigator outfit.

What you need:​

2 uncut rubies
7 iron daggers
6 planks
8 balls of wool
2 buckets
10 feathers
5 boots
2 gold amulets
3 bones
5 pike
7 bronze mace
Fire runes
Earth runes


How to get it:

You MUST have these items in your inventory when speaking with them.

Talk to RODDICK in Lumbridge.
3 pike
2 buckets
10 feathers


Speak with the ranger/shopkeeper at the Varrock range shop.
2 gold amulets
5 leather boots
8 balls of wool


Falador Party Room 2nd floor; Megan.
6 fire runes
3 bones


Falador Hairdresser.
3 planks
4 earths
7 iron daggers


Al-Kharid Skirt Seller.
2 uncut rubies
6 bronze maces
4 fire runes


Duke Horacio, Lumbridge castle, 2nd floor.
2 pike
1 bronze mace
6 earth rune


http://runescape.wikia.com/wiki/Investigator's_trousers
^
What it looks like

​

 

Any chance of you posting pics of the investigator's outfit? I feel like I've seen it, but am not sure.

 

How long is the outfit actually available to get? I've got it on one account so far, but wondering if I should get it on others before I miss the opportunity...

 

Good job, but isn't this a guide? I think it belongs in the guide section...

 

I'm going to do this later, thanks.