The only thing necessary in casting any magick is you.
Will, focus, belief and knowledge. If you're not naturally adept in throwing magick, you will need to practice the basics of energy manipulation--charging, shaping and sending--as well as the basics of your own spiritual wellbeing--grounding, centering and meditation.
Ingredients, correspondences, and ritual are all just tools--a way to mentally accept the change/goal we wish to make. Magick is mind over matter in essence, but some people need to see something in order to believe it, which is why we use spellwork/rituals.
Sigils, symbols, and representations of elements are there to facilitate a bond/connection with the energy of what they represent. This is when you desire the energy/help of external sources in your ritual. When you are evoking or invoking the properties of these subjects. Choose wisely and learn all you can about what you involve in your rituals/spells before using them. Just because you like, for instance, that the spirit of fire can bring forth passion, it can also bring forth lust and aggression. Considering this, you would want to use something else, such as earth to stabilize these characteristics in order to control them better. Many people use all four to insure balance of character.
But remember, these are not necessary, they're extra "support"
Words, sounds and music meet our auditory needs. They bring our thoughts and emotions into alignment with our wills. You don't need poetry or anything long and overcomplicated. Later on, if you want something like that, you can research the power of sound so that your spoken words provoke your desired result. Think simply for now. Two lines. To the point. Memorize it, chant it, feel it, focus on it.
Colors and tools, clothes, jewelry meet our visual needs. Colors associations are both psychologically reactive to our mood and produce an environment that connects with our work.
Actions make us feel as though we are physically productive/making a change. This is called "sympathetic magick". We do things physically in a metaphorical way to reflect the goal we wish to accomplish. It's all about the symbolism! Deep stuff. =)
Specific times, herbs, etc are a way to rationalize that these objects will help us (giving us more confidance and boosting belief). Specific times are astrologically significant. They can aid you if you like, but they don't HAVE to be used. If you ignore their existence, it doesn't harm your outcome.
Herbs and stones, like symbolic representations/sigils render certain energy that if chosen carefully will aid your work.
These are all ways to help our mind and emotions and some give energy assistance to our magick.
I'm not without that need for ritual at times, but they are very simple and I rarely write them anymore. I perform rituals intuitively (unplanned). However, when my emotions are strong about a subject, I don't need anything other than the key ingredient (myself).
So writing spells successfully is about knowing yourself and stimulating the mood and focus you need based off of the way your mind works. If you choose to make it more complicated than that, then it becomes more complicated and you'll need to research. Do what feels right and what makes sense.
People tend to not understand that magick is primarily about mind and energy. So the most important thing is not which direction you cast a circle, if you cast one or not, or what items you use--what matters is that you create an environment that sets the right mood to focus your mind on one solid thought (your goal being accomplished), that the ritual/spell makes you feel comfortable and confidant, and that you are able to concentrate throughout it.
The absolute #1 thing so many beginners overlook, you must build the right energy within yourself and put it into your work for it to manifest. And you must will it with total undivided attention as you project your desires .
You build energy all of the time. If someone truly insults you, your anger rises...your adrenaline may start up, you rage out! Now imagine if heavy metal was playing in the background, and you were wearing red or black, and you had friends behind you (big ones lol). Look out! The battle will begin! Action will take place and you'll be pumped for it!
Well, let's step back away from the violent situation, and just look at energy. Anger is the easiest energy buildup to associate with because let's face it, we all get angry. But preparation before a sports game, speech or competition, all builds up our energy and enthusiasm or determination to get what we need to get done. Now harness that, focus it, and project it and you have magick. A situation occurs, you want to do a spell, your will for it builds and your psyched for it. You play the right music, use colors to set the mood, collect your friends (the elements, a deity, powers/spirits of through sigil representation) and you're ready to roll. Just be sure your friends get along and all things have a sort synergy within them, and you'll be fine.
Hehe, I'm in a writing mood. Sorry for the novelette. ;-)