Welcome! The Yncarne is such a cool model isn't it.
As to what you should get, it depends on what sort of games you want to play. If you are going to be playing tournament games and want to push for the win I would select from this list:
Other things you need to make a tournament legal army.
If you are playing friendlier games you can take pretty much anything in the eldar army as they are all pretty good in relation to most things in other codexes. Dark Reapers, Wraithguard in a serpent, Dire Avengers, Crimson Hunters, War Walkers, all varieties of grav tanks + others are all easily strong enough for most friendly games.
On top of that there is the new Ynnari guys too, meaning you can take basically anything from Eldar, Dark Eldar and Harlequins.
Enjoy the new Eldar, you have joined at a good time!