This is why I am confused. If I believed in the almighty power of Fanta, and truly believed in that, we both know it's not going to have any effect or power in my spell casting. True intent or not.
But to believe in a higher power, it's vague to me, as that's to say I could choose anyone to put my faith in. That seems to be open ended where made up idols and other such stuff could come into the fray.
By this do you mean that you are an atheist? Or simply that there are so many beliefs in the world that you don't know which is true?
If you don't necessarily believe in a Higher Being then there is no one for you to invoke, according to what you believe. If you believe there is a Power greater than yourself in the world, whether you think it has a name or not.... or if you think it might not necessarily be associated with any religion, etc. then you can petition to that which is greater than yourself.
If you DON'T believe in any of these entities, then I see no need in petitioning them. Instead you would just attempt to cast a spell from your own personal energy.
Also, the candles and other items used in spell casting, if as I've read they don't actually have any power in the spell itself, then why not simply say a prayer to a higher power for your wish to be granted with clear intent and belief, and presto it's done?
People light candles in different cultures and religions for different reasons. Some light them, as well as incense, to draw spirits or angels. Some view the candles as an act of devotion to a deity. Some believe that the incense are for the pleasure of a deity, and others believe that it's for the caster or the spell itself.
You can say a prayer, there's nothing wrong with that either. From personal experience, if you know how to pray, and all the conditions are right it is just as effective. However, there are some people who don't believe that it is, or that they should directly make changes in the world around them using their personal power. Views on this will vary.
When we cast a spell, other entities aside, we're draw on our personal energy, our faith, power, belief, and so on. One of the most popular views is that spells using materials are much stronger because our energies are put into those things we use as well, thus candles and such being charge with our intent. And so... a candle that is charge with our intent can help to carry out a wish or prayer. It's another physical object containing a desire. (If this makes any sense to you.) Regardless, that energy and power is still coming from within ourselves.
Can you imagine what would happen to the world if people fell in love every time a pink candle was lit?
Colors raise different emotions in us. And therefore, from my view, it works with our sub-conscience in that respect. Additionally, there is the belief that colors have certain vibrations beyond how they affect human emotions.
So, in essence, by using the materials, you're putting your personal energy into materials which are appropriately associated with your cause, and in some sense... it enhances your ability to manifest your will in the world. At the same time, I've had prayer where I've drawn enough energy (which were under the right conditions) which worked much faster than most of my spells. Additionally, I've willed things to happen without the use of any other items. But to be in such a state, for me at least, is rare. And regardless of what method you use, you're still drawing on your personal energy and your faith.
This isn't to say that materials have no properties of their own, but rather that in spell casting it is the person, and not the things which makes things happen.
It's not really about choosing what to think so much as it is about knowing what you believe.