The DLC gives you instant access to the new operators as soon as they are released. Without the DLC you need to wait for a week and then buy them for 25K renown (currency earned in-game). It’s also grants you 600 credits (paid currency).it gives you 10% extra renown for the games you play and almost (I think) everything is 10% cheaper in the store. You also 2 extra daily challenges (completing which gives you renown) and you can 10% extra Alpha packs %. The Alpha pack system is basically a system where you get loot packs which contain 1 cosmetic. Winning a game rolls your chances for an Alpha pack. Completing a game increases your chances slightly, however if you win, the increase in chance is applied after you roll it, so if you don’t get an Alpha pack you start with 3% (or 3.3% in the next game).
The season pass also gives you 1 exclusive head gear and loadout for each new OP.
I don’t recommend getting the season pass 2 because you’ve missed the timed exclusivity for all but 3/8 Ops. And the extra 10% renown isn’t worth it for only a few months. However, any other bonus I mentioned is still fully applicable.
Apart from that, every Op and most cosmetic is purchasable for Renown, which you don’t pay a penny for. However, buying a non DLC OP from a CTU that you already have an OP for will be more expensive. So for exam, all vanilla Ops start at 500 renown. If you by an SAS op for 500, the second SAS op you buy will be 1000, but any other non DLC Ops will be 500 still. All DLC Ops will always be 25K unless you get the appropriate season pass.
All maps are automatically available to everyone as soon as released, however only 10 are in the Ranked mode map pool, while all but 2 are in the Casual map pool. The 2 remaining maps are only available in Custom games atm as they are being reworked.