Congratz for the purchase which variant and color is it ???
Make sure ur battery terminals are properly intact as mine were not, Check ur sunroof working properly make sure ur boot lid closes properly as it happens sometimes with new cars, chek ur nav system(if u hv got nav variant) rest i guess u ll be good to go.
As for upgrades, cosmetic changes are ur personal choice and about tyres get urs changed ONLY if u find any genuine tyres becoz here in my city shops r full of smuggled expired tyres with tempered expiry dates this is why i have not changed them yet and they are absolutely fine.
As far as polishing is concerned use only branded products(waxes, detailers, microfibre cloths etc) not those cheap cosmic or formula 1 polishes, And as u mentioned u r a noob in such matters then just wax ur car after washing it (wax it twice a month atleast) and for that follow the detailing thread here on pakwheels or just google for tutorial videos on how to wash and wax ur car.
Do share the pictures and ur experience after u receive ur car