Deciding what items to get on Ogre is cake. You will start out with mana enhancers, because your mana is complete garbitch. Then we will focus on powering your hero up. We want Ogre to be very useful to the team and not useless. We get consumables to increase survivability, and to allow us to farm more. If you don't farm enough, it will be harder to participate in teambattles and do a lot of good. Creeping is something Ogre can do well, unlike most int heroes. This is because of his high strength, and his ignite skill. Fireblast should not be casted on creeps, mainly because its just not needed. Ignite does the job much better then Fireblast.
Arcane Ring
Arcane Ring is a very powerful mana regeneration item. This is what you should replace flasks with. This is such a great item if you have teammates that also need mana.
Bottle
If you aren't farming well, and or you need some extra health because of constant nukes, the bottle is right for you. It is very easy to buy and will give you most of the mana you'll need up until midgame (do not buy this and arcane ring, only choose one.)
Boots of Travel
I didn't put this on the core because you don't necessarily need it yet. Enemies haven't gotten BoT yet (or possibly even Power Treads) and it's not lategame, the point where you must teleport and help the team in all lanes. I say this is good, but only when you think you'll need it, such as your enemies are mass pushing all lanes constantly.
Linken's Sphere
Linken's Sphere is a very Situational item. It depends on if there team has nukers, and a lot of singletarget nukes. If they don't, its pointless. I recommend other items before this, it's not that worth it getting it first, so don't.
Cost: 5,175 Gold
Radience
Nice item, however it's not that useful on Ogre. Usually someone else on your team will go for this, let them. This item isn't recommended that much on Ogre. You already have an AoE DoT skill anyway.
Cost: 5,150 Gold
Guinsoo's Scythe of Vyse
Most Useful if there team has a hero like Troll that needs to be disabled in order to be killed. However, it Can be useful against any hero. It it recommended for the disabling purpose, but it is costly; so I would recommend an Orchid before this.
Cost: 5,675
Blademail
Unneeded! Ogre isn't a tank tank in which he needs to buy items to help him with this task. Ogre is a caster at heart, and that's why the items we are getting help his manapool and give him additional abilities to cast.
Cost: 2,700
Necronomican
Almost made it to the bad items section, however, it has some use. Very little, but some use. Its only needed for 1 thing, the true sight. By the time you spend over 3k leveling it up, you could have been building something better, like Guinsoo's. I don't really like this item a lot in general, so it's probably opinion based.
Cost: 2,750 (Level 1)
Cost: 4,050 (Level 2)
Cost: 5,350 (Level 3) -The only useful level and it costs a lot!
Dagon
Useless, period. After your core, this will be very time consuming to get. After you get it, guess what? You have to level it :nuke: . After spending 5k leveling it and trying to make it useful. The other team has tons of life. Besides, this item doesn't really benefit you because you already have enough mana, and it doesn't Multicast. Fireblast has a low enough cooldown, Dagon is not needed. 6 seconds>40 seconds.
Cost: 2,850 (Level 1)
Cost: 4,200 (Level 2)
Cost: 5,550 (Level 3)
Cost: 6,900 (Level 4)
Cost: 8,250 (Level 5)
Aghanims Scepter
Ahh how I miss combining my Soul Booster for you, baby! (Doesn't work for Ogre anymore).
Cost: 4,300
Bloodstone
This item was also on the core build. It helps you a ton in battle, giving fantastic bonuses! With Multicast, getting charges will be easy. This item is recommended though it depends on how you play Ogre.
Cost: 5,050
Shiva's Guard
Another great item on Ogre. This one is a good damager and slower. It's built for team disables. Ogre can use this to chase with, giving it another plus. I recommend this.
Cost: 4,700
Orchid Malevolence
Another disable, except this focuses primarily on a single target. It disables all enemy spell casts, great for other heroes like Luna and Lina. This one gets the thumbs up! This is probably what you want to build first after your core.
Cost: 5,025