Poacher's Dirk + Future's Market IS GOLD EFFICIENT!
Poacher's Dirk
+10 attack damage Unique – Headhunter: After killing any enemy, your next damaging spell will deal 40 bonus physical damage to all enemies it hits (30 second cooldown). Unique: After poaching 4 large monsters from the enemy jungle, transforms into a Serrated Dirk
that sells for Gold 0.
Recipe
Long Sword
(350g) + 150g = 500g
From cost analysis, using a Long Sword as the benchmark for attack damage, spending 500 gold for what amounts to a Long Sword with a passive is only 70% gold efficient.
I think the community in general has agreed that this is not worth it since this item is very uncommonly purchased.
However, with Future's Market, you are automatically allowed an extra 150g +5 per minute.
From my practice, you usually have about 640g after clearing your fourth jungle camp, giving you enough for Poacher's Dirk and and one other item at or below 300g.
( Side note: I like having boots because you have backed early and are going to be counter-jungling. Being able to move quickly gives you the best chance of getting into the enemy jungle ahead of the enemy, and getting back out without getting collapsed on. It might also be worth considering starting with a refillable and upgrading it to a Hunter's Potion at this point. Having the extra sustain is good when you consider the danger you will be putting yourself in while invading, also taking into account how gold efficient this item is as well)
By using the 150g from FM, you negate the extra recipe cost to purchase Poacher's Dirk. This means, Poacher's Dirk is now 100% gold efficient (not accounting for the passive)
"But you are putting yourself negative that 150g and another 50g on top of that"
Three reasons why that doesn't matter.
First, your negative balance only impacts you on your next return to the market. At this point you have only spent the gold that you have earned.
Second, the additional passive that you gain from Poacher's Dirk (or any item you purchase with Future's Market) has(have) the potential to give you enough of an advantage to make up for that gold deficit by allowing you to accumulate gold faster. Early advantage means you can start to snowball. Therefore, it is best to use Future's Market to purchase gold efficient items.
Third, when Poacher's Dirk finally evolves, you now have 25 attack damage and 10 Lethality FOR FREE, which adds up to a gold value of 1100g. Because of the first point, you have essentially only spent 350g for 1100g worth of stats (not accounting for the passive). That is over 300% gold efficiency. There is no other item in the game that is more gold efficient. AND, the time that it has taken you to complete the evolution will have resulted in gold that you can now invest into another item, instead of Serrated Dirk.
+10 attack damage
Unique – Headhunter: After killing any enemy, your next damaging spell will deal 40 bonus physical damage to all enemies it hits (30 second cooldown).
Unique: After poaching 4 large monsters from the enemy jungle, transforms into a Serrated Dirk
that sells for Gold 0.