First car, then I would suggest splitting into important vs not-important.
Important / Good to do
- servicing
- reflush of engine oil
- alignment
- full diagnosis
But chances are, if you're getting this from a dealer, the first 3 items would've been done already. Full diagnosis, usually hard to say. Would you really go ahead and change everything a workshop says needs to be changed? If the transaction is already confirmed, you should just drive for a while first and take note of any weird sounds that may come up. If all is good, then after 5000km, just do a regular servicing and change the engine oil, and ideally gear oil as well so that you know when it was changed. No need to do an engine flush if it drives well, just change the oil.
Not-important
- rear camera parking
>> if you have rear sensors, it's probably sufficient but this is up to you.
- front camera
>> You can buy any kind of snap-on camera that can be attached to the windscreen and run the USB cable to the cigarette socket yourself. Unless you want those 24/7 recording type that connects to the battery, then you need to be sure your battery is in a good condition.
- body kit
- spoiler at the back
- led lighting at legrooms
>> These are not critical. Do these only after you're very very sure of the condition of your car. Budget for this can be redirected to other actual car parts to get a smoother/better drive (especially shocks, engine mounts, brakes, brake fluid).