I can't see my "Left to Spend" amount anymore

The "Left to Spend" feature can be accessed via the Spotlights section of the homescreen:

If you don't see it, or wish to make sure it appears earlier in the list, you will see an Edit button when you swipe across. Tapping on this will let you decide what shows in Spotlights and the order.

Alternatively you can also get to this by tapping on the pie chart at the top right when you're in the account focused view.