So, Adamantite quests are becoming harder now and I'm trying to figure out the best way to use my ore.  Is it worth it to use any on the Starlight?

 

I dont typically use the starlight, but I use the other 5 (MoG isnt strong enough yet) pretty frequently.  

 

Should I just use all my adamantite ore (including the ones I get from the Starlight quests) on the keyblades I use or is it worth my while to use some of them on Starlight?

Starlight is pretty useless imo. There are barely any quests where you need all three types. So I would upgrade any of the other 5, preferably your weakest one to improve it.

Starlight is pretty useless as a neutral Keyblade, the only thing it has more than the others is easy upgrade (atm the only possible +27 Key) and stronger friend slot. As a neutral Keyblade for f2p players, Divine rose with guilted Shadow and Jack is better, and for paying players Moogle of Glory or Treasure Trove are even better with Repliku coming soon...

There will be quests where you will need it so yes.

Divine Rose and Moogle of Glory are the only ones really relevant at the moment. Olympia is really good but is gonna be totally replaced by the Lionheart so theres no real point to invest in that. I would highly recommend not using Starlight. True me, I made a mistake by upgrading it to +25. Now Olympia and Divine Rose is carrying me through the HSC.

Yeah, Starlight isn't as useful anymore due to the way it's set up. Stick with Olympia and Divine Rose, they have more guages.

Divine Rose and Moogle of Glory are the only ones really relevant at the moment. Olympia is really good but is gonna be totally replaced by the Lionheart so theres no real point to invest in that. I would highly recommend not using Starlight. True me, I made a mistake by upgrading it to +25. Now Olympia and Divine Rose is carrying me through the HSC.

The same here I was in love with the Starlight but I haven't realised that the Olympia could goes up to 17gauces.

I won't say that the Starlight is totally useless. It has lower gauges than the Olympia, the Divine Rose, and the Moogle O' Glory as a multi-attribute Keyblade but one good thing I know about it is that all the multipliers are almost evenly distributed in all 5 slots of the Keyblade.

 

This is unlike any other Keyblade. Not even the new Stroke of Midnight Keyblade in JP is like that. So the Starlight is a perfect balance of all attributes and all 5 slots. It is useful in some situations.

 

It's just that we ought to focus on 1 or 2 super strong Medals and put them in the 4th slot of the Olympia and the 5th slot of the Divine Rose, which have extremely high multipliers at Level +25 or +26 and could wipe out enemies in an instant. The Starlight is useful when you have multiple strong Medals. This is what I can say for now.

 

As for the Adamantite Ores, it depends on what you have and what your situation is: your Medals, your skills, your Keyblades, etc. Work through them and you should be able to find out your answer.