Hello and welcome to the forum.
Wraith Host set is an excellent place to start, if you like the look of the models.
Wraith units are typically characterised as high toughness, good army saves, very potent weaponry, expensive per model. In Space Marine terms, they are our terminators, our dreadnoughts, and our titans
The wraith infantry weapons are very short range, so a Waveserpent or two to get them up close early is a very good addition.
FW Hornets look very pretty, and are extremely good value (in terms of points, not so much in $$). I don't use FW stuff so am not clear 100% on the rules, but none of the detachments or formations given in the Eldar Codex allow for Hornets except for your basic CAD (they are Fast Attack)
Warp Spiders are a very potent Fast Attack choice, but the only way to field them in a bound list is either as part of a CAD, or part of a formation containing 3 units of aspect warriors, so if you want to play them, you'll need to also pickup 2 units of troops and/or 2 other units of aspect warriors satisfy the formation requirements. Considering you want the Hornets as well, I'd suggest troops would be your best bet.
Troops-wise, the Windriders (jetbikes) are by far and away the most competitive, and are fast enough to keep up with hornets / spiders / wave serpents. Other options are rangers (snipers), guardians (basic infantry), guardian storms (cross between assault and special weapons infantry), and Dire Avengers (elite infantry). I think the rangers look the coolest, but they are also the least competitive IMO. Dire Avengers are also aspect warriors so could give you some more options on formations other than CAD.
NB: Going down the CAD route would also require an HQ. You could use the spiritseer from the wraithhost, but then you couldn't take the Wraithhost formation, which has some pretty sweet rules. Might be worth picking up a 2nd HQ for more flexibility.