Maraya- ever green, will live in a pot, heavenly blossoms, also grows from cuttings. BUT if you want something to sit under - you're not going to get that big in a pot - the pot would have to be massive to counter balance it falling over.
My favourite trees are jacarandas- you can have them in pot for a year or so before putting in the garden, however you won't be able to sit under it at that stage at all.