I say this because i have played Lux support alot and i do really good but today I had to go Mid with lux and I saw that she was actualy good at mid So I really dont understand what role lux is. Also i her sheid really that useful or is it only useful when you use athenes unholy Grail?
lux is a utility or support mage. naturally all mages will be stronger when played on mid lane instead of support. this includes annie, zyra, morgana and lux because of solo lane farm and xp.
but shes supposed to be able to take both positions.
Lux support is really good with champions that can use her stuns to their advantage as well as she has decent poke herself. Items like 
and 
synergize really well. The only issue I've had recently is the mana cost of E so I personally don't poke as much with it as I did back in season 5.
Lux was originally a mid lane mage, but whether there or in support, you can always build 
if you want late game scaling (Janna I think was the only other support I know of that had it as a recommended item for some reason).
She does not fare well against tank supports like Braum, Thresh, and Bard but excels against Sona and Soraka support.
Lux can go both mid and support, like 
Since she has her Q and E to peel really well, and her shield is alright but not the greatest thing ever.
Just don't be one of those lux supports building some 
itsokbecauseimainher
I'm not sure about her shield though, it's pretty weak on it's own so Athens would be a pretty good idea. I do thing she's better as a midlaner though, but she does work as a viable support in most situations.
I think she fills both roles nicely. I personally HATE playing ADC against a Lux because of the ease in which a good Lux can zone you off creeps. A good Lux support will also not constantly be saving her R to KS the carries but use it instead to butter the enemies up for an easy kill or forced back/tower.
worse than zyra/morgana/velkoz
ps. lux is a mid champion
Lux is a mid laner and a wild card support. In mid lane, she thrives in almost every situation due to her range and scaling. As a support, you should only be using her in scenarios that warrant her use.
What I mean by "wild card" support is that there are those Support who are extremely good given the proper conditions but otherwise are pretty bad at the role.
Lux is one of those, just like 
and... well 
. :p
Where Lux shine as a Support is on her Q and passive. The delete potential at level 6 makes her dangerous against squishy champions and her Q has a very good synergy with certain champions such as Jhin. She is extremely weak against hard engage, sturdy supports or ADCs with dashes.
She is designed to be carry, not a support. Her supporting skills are the weakest aspects of her kit. She also scales significantly harder with items, which are harder to acquire as a support.
Lack of a true hard CC, the fact that her shield is a skill shot, and the fact that her snare is a weaker form of both morg and zyra's means that she really just doesn't match up to other more conventional supports.
There are certainly worse things you can use, but it's a sub optimal support choice, and keeps her from reaching her real potential as a champion.
athenes sound as a bad item on her, build morello instead, it is much better (gives a great mana sustain (the lost chapter for laning and the tome itself for teamfights), gives more than twice more ap than athenes, gives grievous wounds too and also gives the same cdr as athenes, it doesn't give mr, but you don't need mr being a squishy backline damaging support with also an ap scaling shield, not like athenes gives a lot of mr too; note the mana passive of athenes was also nerfed the last patch)
support lux should get sightstone and then build ap damage, she is not janna or soraka
her shield is pretty strong with some ap and is aoe
so support lux it is something like sightstone morello rabandon void staff etc
then, support lux is bad, play support morgana/zyra/velkoz instead
