the legenary edition of destiny 2 inludes
beyond light dlc which was last seasons content (you do have access to the curret season which is season of the lost)
forsaken dlc
shadowkeep dlc
not gonna lie i personally wouldnt opt for this pack as forsaken has become free to all players a few weeks ago and as of the 22/2/2022 forsaken dlc will go in to the DCV (destiny content vault) and all destinations and quests will be unavalible from that (apart from the dreaming city destination)
to get started i'd opt for beyond light dlc as that is the most upto date content in the game and will allow you do all thats needed without having all the other dlc's to worry about to complete, wont lie there will be plenty to do with just the above single dlc, it's on offer too via steam 50% off.
See how you get on with that and if you enjoy it then the next dlc to get would be witch queen but a word of warning that dlc is very very expensive and releases on the 22/2/2022, but oh my it brings so much more new and exciting content to the game, i fell head over heals and bought it, but thats me
bit side tracked, have a look at beyond light dlc (not the upgrade ot deluxe editions) and see what you think, if you get stuck there are plenty of groups out there that can help, i've been there from the early alpha on pc 2017 and have done it all and spent a lot of money on the game.
the base free to play game as it stands has plenty of things to keep you busy, (there are 60ish days until witch queen drops so you have time to do a few things including the beyond light dlc)