Well, you could get a Philosophers Stone or Heart of Gold, which are more often seen on Olaf than Avarice Blade, I just figured since you build a Yooumus, you can buy a Avarice blade. Of course, you can just sell the Philo/HoG if you have no need for it anymore, granting you half of the gold costs back.
Also you can just swap out the last item, its not like you have to follow a exact build.
EDIT: If you get a Gp10 item, do it after M.Razor and Boots, then follow to the wriggles

That makes much more sense. :P

I'll definitely be adding a FoN into the build, but i don't think im going to completely eradicate the Ionic Spark simply because it's what gives the build character, what sets it apart slightly from the rest. As for the gold per 10, i think i'm going to add that into the build for sure, but as such a have a question for you; where?
Getting the brutalizer early is very nice, but i can also see the importance of grabbing gold per 10. Should i grab both consecutively? Also, the statistic it gives other than the gold per 10 is certainly not the best on Olaf, so at what point are his stats well enough rounded to bring this into the build (as it will be probably 5 minutes spent on the field with crit chance Olaf). So to conclude, the same question i asked before; where does this item fit into the build perfectly?

Thanks again for all the feedback! This is my first build on the site, and i really do appreciate it!

~Cyanide2x4

Well I wouldnt switch out the lantern at all, besides maybe a Bloodthirster in late game.
My olaf build(top/jungle) contains mostly: Wriggle, Mercs/Tabi/Berserkers, Frozen, Atma, Maw of Malmortius/Force of Nature, Yooumus/Last Whisper/Edge/Warmogs. I dont find alot of need for Attack Speed,the passive is mostly ok, just getting Berserkers if I know that the team consists more of teamfight CC, where I am running around in my ult anyways.
About the Gp10 items: I know that most junglers have around the same CS as lanes have, but thats not compareable. Jungle Creeps give less gold by far. A creep wave spawns every 30 seconds, with 3 melee creeps(~25 gold per creep) and 3 caster creeps(~20 gold per creep). Also every third wave, a siege minion spawns, which gives additional 25-30 gold. Now look at your creeps. Small camps respawn every minute, little wolves give 5 gold, little Wraiths 4 gold. Big Wolf gives around 30 gold, big wraith around 40 gold.Double golems give together around 60-70 gold. Blue/Red give around 75 gold, but you only get blue like once mostly (unless you have a manaless mid that doesnt need it, i.e. Kennen) and the respawn time is 5 minutes.
So basicly, if you clear your whole jungle, you'll get (92+40+52+60+92) 336 gold (added the smite gold at blue and red buff). If other lanes last hit three waves perfectly (which isnt very hard to do), they'll have ~430 gold. But they'll have more of the same gold giving creeps spawning, while you have the two high reward creeps dead and waiting for respawn.
Of course, I'm not trying to drag you to buy gold items, just giving you reasons why they should be considered.

Hi, thanks for the feedback!

I 100% percent agree about the magic resist, and i'm definitely going to be adding some choices into the alternate items when i get a chance (Wits end, force of nature, etc), perhaps mention the possibility of replacing the wriggles with a FoN late in the build? let me know what you think of that one. As far as magic penetration goes, also very true; the damage won't be nearly as high. Keep in mind however that with the exception of hybrid champs not many auto-attackers will be building magic pen, and many can benefit from an ionic spark all the same. It's function isn't to do a LOT of damage, but it's enough to make a difference in teamfights. It also compensates for Olaf's lack of an AOE effect in teamfight, which is how most tanks / offtanks excel at picking up kills or assists.
Maxing vicious strikes? This isn't as much for the actual jungling (although it's nice to walk away from a camp with more health than you came with), but more so for survivability in team fights. The faster you max it, the longer you can survive and the more damage you can do. Plus it enables you to cover lanes exceptionally well, and rarely require a recall.
Next stop; gold per 10. I dont play at very high ELO (hover around 1300, elo hell is a bother -.-), and this build is more designed for that level of play. ANYWAYS, on to the relevant points, i find that quite often i come out as the exact opposite as jungle Olaf; i have the most farm in a good 20% of my games, averaging around 2nd in overall farm. Given any build, Olaf farms exceptionally well in comparison to other champs at lower ELO. That being said, i rarely feel the need to grab a gold per 10 item. Besides, gold per 10 items take approximately 25 minutes to pay for themselves (see the cost efficiency guide in the previous comment), thus proving largely inefficient on any role other than the support. Seeing as it does fit into the Youmuus, however, i'll definitely mention the option at some point in the build!
Starting boots; i guess it's worth mention in the build, and i'll add it in too. The reason i opt for the vampiric scepter, however, is because Olaf can have over 30% lifesteal at level 1. Combined with his passive and vicious strikes, i have literally never run into a situation where i absolutely need to recall at the cost of missing a tempting gank or letting a tower fall. To compensate for the lack of movement speed, however, i notify my teammates that the first 5 minutes or so are going to be dedicated mostly to farming with perhaps 1 or 2 ganks should the need arise which, although they lack speed, the sustain from the neutral monster camps can generally assure you have enough health upon entering the lane to not commit suicide in the ensuing skirmish.

So there you have it; thanks again for the feedback, and i'll definitely be adding a lot of it into the build! As for the rest, further comments are welcomed because, as mentioned in the conclusion, i genuinely want to learn as much from this build as i hope to teach. Let me know what you think!

~Cyanide2x4

You have no Magic Penetration so most targets will get around 40-50% of the damage from the lightning effect. Not quite sure why you max Vicious Strikes first, considering that level2 already allows you to jungle efficient with a Razor (Spellvamp heals from the madreds procs). Also not sure how long you already play Jungler, but getting a Gp10 item is a must since you are the nearly poorest player in your team, only beating the support. Also Boots are quite better to start jungling since they allow for easier ganks. I would rather recommend you to try this: Boots+Pots => M.Razor => Avarice Blade => Phage/Wriggle => Frozen/Yooumus => Impaler/Spark/etc.. Also I would recommend you to get/try Wit's End instead of Ionic Spark to rack up a bit more than 50 M.Res.

Thanks for the comment, and i appreciate the feedback! :)

I was pretty sure that the ionic spark would be the topic of the most debate in this build, as arguments can be made for both side (taking it and not taking it). As far as attack speed to be cost effective, i'm not entirely sure. Based off of an item cost efficiency guide (link below), i totaled the stats it gives you to come out to a value of 1985 gold excluding the passive. That means that players pay about 300 gold for the lightning effect. That's not a bad deal, especially when you consider the impact it has in teamfights; leashing out to 4 targets can total up to 440 magic damage (110 each) which, as mentioned in the mid game item section, can almost guarantee significant assists on every kill in a teamfight. Not to mention that berserker rage will allow the passive to trigger more and more as the fight drags on.

So to summarize, there is definitely a handful of items that could work just as well in its place, but i wouldn't disregard it based on cost efficiency. It seems to do the job fairly well, but any further thoughts are welcomed. Again, thanks for the feedback!

Cost Efficiency Guide; http://www.solomid.net/guides.php?g=4844

~Cyanide2x4

i would change that ionic spark since you dont have enough atack speed for it to be cost effective