It wants to be a chunky small tree, so ultimately it'll need a big pot. Go up one size now, so it's made some good root growth before winter. Mine are in pots, but they are leafy and vigorous, so I have to pay attention to water and food otherwise they go leggy and starved looking. The pot yours is in is probably a 10 or 15 litre. I'd go up to a 35 litre, and the new compost (a John Innes three, or good garden soil and some home made compost will do fine) will supply all the feed required for the next few months. No need to feed then until next spring.

This tree also responds well to pruning, so you can lop bits off to keep it small. Mine in the garden is about 12ft tall andwon't get any larger really.