Candles are one of the places that I see folks new to magical practice do all the time. For some folks, candle magic is the "basic" spell. There's almost this thought that the candle by itself makes the spell. Like most things here, the candle is a way to symbolize or focus on what we want. Really, proper raising of energy is vital for success here. Layering can be very effective. Candles can be worked with just names, a few herbs, and a lot of intention, but layers here can really help to build it up. Color of a candle is nice, and a particularly easy layer to add. Sigil work, and Words of Power apply as easily to this as anything else.
The first thing that's specific to candles that we need to look at is what's called dressing the candle. That's just where we get our oils and herbs engaged with the candle.
With glass enclosed candles it's a simple as a bit in the top. Of course, layers can be built here by blessing or empowering each individual ingredient. All you need is a symbolic amount. In fact, glass candles that are overdressed, with too much stuff in them can burn way too fast, and unpredictably. They can be a bit dangerous. Don't over dress, it's not needed. Just a bit.
For taper candles or chime candles, anything like that, you'll dress in the oil from top to bottom to attract something, or bottom to top to banish. Then I'll take my herbs in a sheet of paper so it collects, and roll the candle in it. You can knock a bunch of that off as well. Again, the point is a symbolic amount, and too much will make the candle act unpredictability.
Pillar candles can be done in either of the above ways, or you can drill a hole in them to load with a bit of the herbs.
Figural candles can be done any of those ways, as well as leaning into figural candles as poppets.
Nothing wrong with commercial oils for this stuff, or making your own. That said, if you're dressing in herbs as well, a simple base oil will do. Sure, that's a place to add layers.
Raising energy and some time focusing on your intent is vital to candle work. Often, this is what makes the difference for candles success or failure. Other layers are great, and the simple candle techniques here can also be one layer in a much larger ritual.