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Good news - that tree is much better than I was expecting - but get that goofy wire off of it because it isn't doing anything. You will want to wire it properly to get those branches to sweep down like a mature tree in nature.
Bad news - the soil is very bad and the tree is in need of repotting. Don't do anything now (too early in the year) but wait until it gets warm outside and repot your tree into a better soil mix that is most inorganic (pumice, lava, etc). There are tons of threads on the site where people discuss (and argue about) soil mixes.
In the short term, whatever you put over the top of the soil won't really matter because you will be repotting in a couple of months. You want something to keep the top of the soil moist, but not saturated. If you don't have an inorganic mix handy, I would use pine bark mini nuggets or something similar.