I was given a serissa back in 2001 in exchange for taking care of a friend's dogs while away on a business trip. I probably never would have anything to do with serissa bonsai, since I know they are notorious for being difficult to keep. Such has not been the case for me with the species I was given...one tree has become seven which are now planted together in a forest. I have used the "clip and grow" method for these trees with good results. Their growth habit is such that directional pruning can give the trunks and branches interesting movement. I've never applied wire to my trees and haven't been tempted, really. They are fast growers and when happy they flower profusely. They grow as bushes in their native habit, so just about any style could be applied to them. Informal upright, informal broom, oak style and semi-cascade are a few that come to mind.
Serissa are used fairly often by the Chinese for their penjiing plantings. The impression I get when I see one is that of a pastoral tree growing in a meadow with a stream or pond nearby. Their trunks can develop mature bark in just a few years and they often will develop interesting nebari without any effort beyond removing overlapping roots.
I used to be indifferent about them but have developed a fair amount of respect for them over the years--they have an undeserved reputation as serious bonsai material that I'm sure will disappear with time as more people try them purposefully or by accident.
I had unusually good results with serissas when I was selling trees. They were in dappled shade outside all summer and all of them bloomed profusely. Of course I did not keep any, so not much more to offer than that.
I am just using the pebbles as a top dressing. I am using a mix or perlite, sand, and wood chip/organic for soil. I have it on my covered back patio which unfortunately only gets light from the north. Should that be enough light?
Ichigo, it doesn't look too bad so you are on the right track.
Prune for a style, then use the clip and grow method, it works great for these. Don't overwater with the soil you have, and you should be ok.
Also if you are looking for growth, the bonsai pot isn't the best place for it, also watch during the heat, small pots can dry faster than you would like. I have a tendency to put these in a somewhat larger pot than normal, if for no other reason the roots can grow quickly and fill a small pot.