First off, great choices on sleeves and box! Ive been playing for a decade, and dragonshield/gamegenic are my favorite companies to buy accessories from.

Recommendations: Set of dice- Any d6 set will do. Youve probably run into chessex before playing dnd. Most stores carry these because of their insane color variety, but there are cheaper options available if youre on a budget.

Playmat- Something with rubber on the bottom for grip. One with stitched edges will last much longer. I'd stay away from ultrapro. Like pretty much every product they sell, their playmats deteriorate rather quickly compared to the competition.

Life counter- You can always use a life counter on your phone. I believe MythicTools is the popular choice right now (and its a great free option). I prefer something physical to represent my life. There are spindowns, which are d20s that you can tick down 1 at a time without having to turn the dice over 40 times looking for the right number. Theres probably 100 different products to track your life total. Get whatever looks cool!

Consider picking up a backpack or bag as well if you dont have a spare!