There is infinite ways to defeat them ...
Depends a lot on what level you are, what spells you have, what consumables you have, and what equipment you have.
Fighter at level 5 ... with action surge and haste potion is able to attack ... six times in first turn if i count corectly ... wich alone is just devastating with Wyvern potion, even for Githyanki.
Its true that loosing initiative is basically death sentence for your frontman ... so if you really feel lucky with dices, you may send down your high-dex character to negotiate (prefferably with misty step scroll to get them to safety fast).
But bread and butter is positioning here ...
High Ground makes huge difference and it gives you one or two turns before they reach you.
Or HUUUUGE damage, if they port on you and you manage to shove them back down.
Spike Growth is spell i love a lot ...
For eason most enemies (including Gith) decide to run across that, rather than avoid it ... this is especialy kind from Gith, who should be able to jump over full length.
Another superusefull spell is heat metal, especially if you have crown that gives you another BA, allowing you to cast its Bonus Action damage twice per turn (thrice if you are a Thief) ...
Its not a bad idea to send pets close to their archers, so they either need to waste one attack on them, or have greatly reduced chance on hit.
For some reason they often dont risk AOO. Even as trivial as this one.
If you still have spider egg, this is great place to use it!
Obviously you cant go wrong with sussur weapon, or amantine armor here ... oh and speaking about armor, make sure your frontman have metal helmet so Gith dont erase them with two critical strikes.
That should do for basics ...
Is there any particular tactic you would like to expand uppon?
