https://www.reddit.com/r/totalwar/co...for_total_war/
https://www.strategygamer.com/articl...rhammer-2-dlc/
It mostly depends of what race or faction you want to play.
There are completly new races (wh1 - Norsca, Beastmen, Wood Elves, Chaos Warriors / wh2 - Tombs Kings, Vampire Coasts) as well as legendary lord packs for existing races.
The legendary lord packs also features Regiments of Renown for those factions (RoR are elite variants of units, generally better than non elite but you can only have one each) which is something to consider. If so, the first dlc released for x race contains MOST of RoR (further legendary lords pack contains 3 new ror because it also brings 3 new units for each factions). Here is a list for unlocking most of the RoR (each also brings new units for the two factions and one legendary lord for each faction):
Warhammer 1
- The King and the Warlord (dwarves and greenskins).
- The Grim and the Grave (empire and vampire counts).
Warhammer 2
- The Queen and the Crone (high elves and dark elves).
- The Prophet and the Warlock (lizardmen and skaven).
As for my opinion i suggest playing first, if you like the gameplay then buy the legendary lord packs for race you like to play (While the race mechanics dont change the legendary lords start at different position and most have some special mechanics included). For example the Eshin from Shadow and the Blade dlc is a stealthy rat faction which has expensive recruiting off non stealth rat units while buffing stealthy rat units so it guide for different playstyle, because economy in early game would not sustain the non stealthy rat army.
The Race dlc give 2-4 Legendary Lords and whole new race to play, with unique mechanics, units, etc.
What to avoid - Wood Elves, Chaos Warriors and Beastmen - those are basically the first race packs and it shows. Wait for rework (greenskins were in similar position not so long ago).
Also, watch (it is long video but really go into details and specifics)
https://www.youtube.com/watch?v=WA_iXKhoujA
- - - Updated - - -
They dont change now.