If you are considering getting this game, make sure you buy Forsaken. The game was alright at launch but the next two dlc's were just average. D2 got a lot of slack from the D1 community and it's perfectly understandable. Forsaken really did take things to another level. The new areas to explore are absolutely breath-taking with beautifully crafted music to follow you along wherever you go. PvP is fun (when not dominated by a broken weapon or armor piece) and offers a variety of ways to play with others.
PLEASE find a way to play with friends. Playing alone does offer tons of hours of discovering lore, playing through campaigns and doing PvP via crucible and gambit but the raids and strikes are where the game shines. And you really need friends for that so join a clan and meet team up with fellow guardians.
update: Destiny 2 is now FTP so that should incentivize you to get your friends to join. Although this doesn't include Forsaken or Shadowkeep, you still get access to some great raids and multiplayer fun. I'd still highly encourage any Destiny player to purchase Forsaken because that is a peak in Destiny's history that I'm not sure will be peaked again (even though Shadowkeep has some great new features)!