@angesradieux - Nice Serissa. Let it grow or chop? All depends on what YOU want. Bonsai spend much of their lives 5 or 10 times taller and wider than their final height as a "finished" bonsai. We usually let them grow out until the trunk is the diameter we want in the finished tree, even if growing out means letting it get 6 or more feet tall. Right now your trunk is still pretty thin. I would let it grow out, until it is time to bring it in for winter. Then cut it to just barely small enough to fit into your light garden or winter area for the tree. Back out in spring, and so on. You need at least a half inch trunk, to make a bonsai, one inch or larger would be cool, but Serissa tend to have thin trunks, unless you can let them grow out for a decade or more. It is the number of leaves the trunk supports that makes it thicken, not the height of the longest branch. You can "hedge prune" it for a few years, to get it bushy and supporting a lot of leaves, this will thicken the trunk. With deciduous trees that bud back well, it is very much the volume of leaves that thicken the trunk. (conifers the process is more complicated) Once you have the first 3 or 4 inches of trunk as thick as you want them, you can remove all the branches, reduce it to just the trunk, and it will back bud all over, giving you the branches.
Reading: Brent Walston - Growing Trunks for Bonsai (Evergreen Gardenworks website), Walter Pall's articles on Hedge Pruning for development. Walter Pall's Blog. Read the many articles about the use of "sacrifice branches" to thicken specific areas of trunks or branches.
I'd let yours grow a couple years more. It will give you more branches to choose from when you do finally decide to style it. And you will be able to take a 4 foot tall Serissa and cut it back to 4 or so inches and it will back bud on old wood.
Anything you cut off can be rooted to make more Serissa, the root easily from cuttings.