Learning how to make your own spells, you need to master the various spell components that go into building a ritual. I am talking about the mix of "stuff" that gets used rather than the words and the intentions.
Using herbs in spells goes back centuries to the age of the wise woman who made medicine from local plants. There is great power in herbs, both physically and magickally. Most people use dry herbs because they last a long time and are easy to store, but if you are able to use fresh, that's even better.
Stones and crystals can look glorious on an altar, but they also have great energy inside them as well. And unlike herbs, they're not used up after a spell. A piece of stone can last forever, and never run out of magick.
You can recharge a crystal by leaving it out in moonlight overnight periodically, or rinsing it in naturally flowing water (a stream, not the tap)
Candles not only bring the energy of fire to your spells, but you can also choose your colors based on your purpose. Scented candles are fine as long as the energy of the aroma matches your intention. Manufactured candles obviously don't take this into account when matching scent and candle. White candles are great as a multipurpose option, and you can use your own oils to scent them.
Oils and Incense
You are really using the same energy in oils as you are in herbs, just in a different format. It's still plant energy, so you can use any good herbal correspondence chart to figure out your oils. They work better than herbs themselves to anoint candles or even your skin, and they tend to be more aromatic. Incense goes along with oils in the same way, allowing you a different form (air and smoke rather than liquid).
Using the spell components already mentioned can easily be enough for your spellcrafting purposes. But an altar with a few tools can be a powerful one. An athame, chalice, cauldron or wand can all have an important spot in your spells though they are not crucially necessary. I have another page on altar tools that will give you more details on them.
These are your basic spell components, though you can always adapt any spell to use what you have on hand. A good correspondence guide will let you know which of these components will fit your intention, and how to make replacements.