There are a couple of considerations re the best way to arrive at your target ht. One of them is, we want to get rid of the stake and make sure the tree is self supporting. Light is a key issue and the primary determining factor in the thickness/strength of the trunk. If your tree is self supporting, you can prune off the top at about 2/3 of your preferred ht & start building branches, allowing the canopy to provide the last 1/3 of the ht as it fills in.

To achieve this, you allow all branches to extend to 4-5 leaves, then cut the branch back to 2 leaves. From each of those 2 leaf axils (crotches) a branch with form that you allow to grow to 4-5 leaves, then cut back to 2 leaves again. This is called secondary, then tertiary, quaternary, quinary, senary ..... branching. In numbers, it means you start with a single branch. By cutting it back, you get 2 branches. Cutting them back gives you four, then 8, then 16 branches ......, all from a single branch. Of course, you only keep the branches that enhance the composition, but within 2-3 years, you might be presented with dozens of pruning options instead of only 1-2. This technique for increasing branch ramification is what allows us to have little 12" tall bonsai trees with dozens of branches and hundreds of leaves. The technique is readily applied to almost any houseplant that branches - even if it only 'eventually' branches. I'm always pinching/pruning to keep my houseplants tidy and compact.

This is a Ficus b that I'm hoping will eventually be a decent bonsai. Note how healthy and dense/compact the foliage (that badly needs pruning) is, and how the leaves have reduced in size because of the large number of leaves. I'm just waiting for the 5-6 trunks to fuse into a single trunk, which will add to the illusion of age. This picture is about 3 years old, so the planting has progressed quite a bit since it was taken:
{{gwi:43081}}

The things for you to focus on now are the soil, watering habits, a nutritional program, and siting it in the best light you can, and where the soil will remain between 65-75* How fast you progress depends on how well you're able to manage things cultural.

Al