Get them to throw in the dropper post and tubeless conversion for nothing. Apart from that there's nothing that would require an immediate upgrade. Then of course you want shoes, helmet, some baggy shorts, gloves, a hydration pack, a multitool, some spare brake pads, a small pump to fit in your pack, a big pump for the garage at home. Save your leftover money to replace whatever you break or wear out first on your bike. After riding it for a while you'll also figure where you might want to spend any upgrade money.
