Portraits, are a good subject area to learn with your G9 the large LCD screen makes composition a snip, the Live view shows pretty much what you are going to get and hopefully you can have another go if your model is willing or the image is not quite what you wanted.
Portraits are also one of those subject areas news and documentary photographers need to master as looking in the national papers recently, there seems to be a very high percentage of images that are portraits which is strange, considering how much in the world is not getting shown in the way of wars, famine, joys, accidents, climate change… (and I could go on)
The magic of the portrait is the gaze back to the viewer and it has kept many fine art practitioners busy over the centuries, so you will be following in good shoes and for a twist you can also take a look at environmental portraits, macro, abstract, etc.
The grid view on the G9 can either be a hindrance or a blessing as an aid to your work, some people will find that to much information like the grid lines, histogram are in the way and distracting. while others will like the way the grid helps them frame the composition and keeps lines from converging in the background in environmental shots, so try different combinations to see what you prefer. You could even save the settings in the custom control C1 or C2 if you use them a lot (See G9 Resources for some help if you need it)
The thing is there are rules to composition that you can follow, but then you can also break them to make for interesting views, so it’s not a thing you can get wrong; but you will be the judge, if you like it then its good.