The tree looks good and healthy. I would not repot this tree or add soil. If you haven't, the tree should be fertilized. I use Miracle grow but at half strength or weaker depending on the specie. For this tree, half strength. There are commercial fertilizers for bonsai available.
There are...
The tree does not appear too large for the pot. I am unsure of the specie. Do you know what kind it is? How long have you had this tree? It is quite old. It reminds me of a privet.
Pina Colada. This bonsai has not been shaped. My wife found this being sold as an annual for window box plantings. It's a perrenial shrub that has blooms and a wonderful smell. Plants for bonsai can be found in many places.
Kimmi tells me that our Walmarts are Super Walmarts and that only Super Walmarts have the garden center. Regular Walmarts, she says, do not have the garden center.
Good luck with the seeds. Take the time to research how to germinate them. Many seeds have special requirements in order to sprout.
The cere is in shadow, but it does appear to be a male. The ceres on males are either, most common, bright blue or pink, not as common. Hens are whitish blue or tan/brown depending on age and condition.
Every Walmart I have been to, and that's a lot, have a gardening center and sell bonsai...
Not laying eggs does not mean it is a male. Parakeets/budgies nest in wooden boxes or something similar. People have given my older parakeets they thought were males because they had not laid eggs. In the right environment they soon nested and raised young; one was ten years old when she laid...
Your parakeet are very pretty. Are you positive they are both male. The top picture is a male, but the bottom one I can not see its cere.
What do you think of this plant/bonsai. BLUE JUNIPER.
It has a very interesting twisted trunk, but in the picture it does not show up.
As long as the wire is not wrapped tight you can leave it on. Often I do leave it on over the winter; depending on the specie. Fast growing species can have the wire taken off fairly soon. Slow growers need to stay wired longer. How's your oak tree? Any luck with the budgie picture?