It's a 3 year plan in Adelaide. There's a "tough as old boots" Jamaican lime in behind this two year old Imperial mandarin.
1/ don't plant in the cold
2/ don't disturb the roots
3/ plenty of sun
4/ plenty of water
5/ fertilise monthly in late spring through autumn
6/ foliar spray zinc/manganese once a year
6a/ perhaps some very expensive iron chelate once or twice a year
7/ use confidor maybe every six weeks to stop your leaves curling from thrips
8/ your fresh green leaves in spring and summer are your future. See above, the old dark green to the left will soon be pruned at the trunk
9/ in winter don't let the roots get too wet and cold at the same time
10/ whatever you do, keep leaves on it. Don't be in a hurry to prune too soon. I've never seen one recover from bare stems.
11/ I paint the sunward bark with any waterbased paint in spring to reduce sunburn.
It's worth persevering, they're tough and rewarding once they get through their fractious childhood.