There's no cheating in using nursery-grown plants to start with. Starting with seeds is cheating yourself by dragging out your learning curve. Jump in, man.
Growth rate in any plant is a classic bell-shaped curve, where growth is dependent on the amount of photosynthesis the plant is capable of. Loosly translated, the amount of leaves or needles, = surface area of green + sunlight = rate of conversion.
You can have an established bonsai by the end of the day, and another one tomorrow. Why wait?
The wintering of seeds to get them to germinate is called vernalization. It is species-dependent. Some seeds require it, some don't. You can do the research, or guess, but that's not gonna get your hands practicing the technique, which would be your goal, yes?
Boxwood is a neat little tree to work on, creates a very traditional tree-like canopy, in miniature. Junipers, cedar and some pine for the classic old, windswept appearance. The choices are unlimited.
The trees, if they are genetically pre-programmed to be large trees, are kept dwarfed by seasonal root pruning and transfer to new containers. Since the plants are to be kept in small containers, the watering schedule is critical. Let em dry out, they're dead, as is all the work you've put into them.
Cloning trees via cuttings is kinda technical, varies from specie to specie and and is generally done using new spring growth. Also requires climate-controlled conditions with all but the most spontaneous rooting species. In Vitro propagation is restricted to lab geeks with a greenhouse. Keep it simple, dude.
