You basically start mana boots to give team mana and eventually switch to aether and tranqs when you recieve all parts that are needed before needing to break down mana boots. This insures team getting mana and farming to the highest potential. I only listed these two as the only core items because the rest of your game is REALLY situational.

Glimmer, Force Staff, and Euls are obviously dependant on helping you team in the best possible way. Use euls for catching people or dispeling off yourself. Bonus points if its used against a Legion Ulti from the other team. KEK Glimmer is good if the opposite team doesn't use detection very well. Also good for repositioning or helping other team members escape. Force staff is honestly my favorite out of the 3 and is always helpful to use for your other teammates. Always really helpful to save important cores. :)

I personally love going Boots of Bearing. These are always good to help take down towers faster and overall more speed like sanic is fun. If you already have someone making drums tho maybe pass unless you can work with each other so you don't have 2 drums at once.

Mwilky also loves herself a vlads game. I personally suggest only making in 2 occasions though. 1. Your 3 cores are physical build, or 2. You have a sniper on your team. I don't make the rules. Vlads and Sniper is just my favorite combo. :)

The Shard vs Aghnim's Scepter: Shard is good for teams that don't push together. Aghs is good if the team is always on top of each other. I get aghs to save my cores and throw my frost ball on all of them. I use the shard to take out a single core. Especially useful if you are getting chased by a core on the opposite team without your own team to save you. Pop your shard, use frost ball and then gaze them back to the ice spear and if they're still alive use frost blast to end them. >U<

Other optional items:

- Aeon disk if you are getting 2-5 shot and need a way to survive the fight.
- Pipe if you need to help team with magical dmg
- Spirit Vessel if you need to help do dmg on big tanky guys like Bristle, Bear, etc.
- Meteor Hammer mostly for the memes but if your sitting on money and need to take towers it could be an okay choice.
- Rod or hex for more additonal cc.
- Shiva's if no one on your team is making it, you are in need of armor and you need the enemies to slow down and slow healing.
- Lotus also if your core needs it and you also need armor is generally when I'd make it.
- Eblade if you or your cores need it, especially useful against void.