Hey nc,
so the elves at the moment are a rabbit hole of different splinter factions that highlight the ways you can focus your army. I myself am fond of the Order Draconis units that were formerly the really elite cavalry and dragon riders (see Caledor), however creating an army purely out of any this faction means my armies are tailored around reckless banzai charges and hoping one of my class rockets can make it to the enemy backfield intact.
The more magic focused Eldritch Council elves, including the (Power Rangers Super) samurai, are able to throw out useful support while the Swordmasters are a one-way flowchart to turn skaven into hamburger meat. The price of such utility, however, is having pricey battleline units, so prepare to be outnumbered.
In most cases the elven subfactions have some form of force multiplier they gain from being purely fielded with their own members - Dragonlords allow all their keyword units within range a certain range to
reroll all failed hits in cqc. Not one of this guy's melee weapons cause 1 damage or have a rending value of -, and he gets 'roid rage from the Order relics in Pitched battles. Like with the Council the cavalry battleline units are expensive, small sized, and only above average, so use them wisely.
the reaver cavalry packaged in Island of Blood/Spire of Dawn are one of the few non-legacy elven units that are 100% battleline, and can provide ridiculous amounts of average shots while keeping their maneuverability (they can move, shoot, and run 2
inches afterwards; perfect for hit and run tactics).
from my personal experience you can get the most out of elves by either going full synergy, focusing on a specific faction, or you can focus on their elite units. Swordmasters and White Lions are, compared to many seraphon units, good sources of constant rending attacks. Dragon Blades can, dice allowing, cause as much as 6 damage per model on the charge (the champion can go up to 8), creating a high threat blitz section.
In short, your Aztec Space Lightning Lizards form the core of the army and game plan, while the cream of the elven crop amplify particular areas. Use elves for their utility and they should deliver.