Most of us here know that the best spells are your own; for several reasons that I am not going into at the moment. Here is just things you may want to consider before you right your own spells.
What supplies do I need, or do I even need any?
Are my supplies relevant to the spell?
Could this spell backfire on myself or others badly?
Am I able to cast this spell in a way that is effective?
Do I have the correct mind at the moment to cast this spell?
Do I really 'feel' this spell? Do I have strong will towards this spell, whether good or bad?
1. Supplies
Supplies are things that could possibly help make your spell more potent; however not all people use them. Some just find it easier to simply say the spell without any supplies such as incense, candles, a wand, etc. This is intirely down to the caster; and their intuition if they need anything.
If you do choose to have supplies, make sure they are relevant to your spell. For example, it would be quite unusual to buy a bright orange candle for a money spell. (Money spells are usually associated with the colour green.) However, if in your opinion you think the colour pink has connections to money, you could use a pink candle. It is all down to your opinion, and what links you as a person make.
Will in a Spell
You noticed I included in my questions ''Do I have strong will towards this spell?'' or something similar. This is because, in my personal belief, the more you want something, the more it is likely to happen because of the way you strive for it, out of pure emotion. It is more likely a spell you dont really have your full will behind will not be as effective.
For example, magick has no colour. Yet we brand it with labels such as 'black' and 'white' to help with easy association. But of course, it depends on one's views. What one may view as 'black' magick, another person may not see as 'black' magick.
Revenge spells would be a good example of this. Some people say they are good because they get revenge if somebody has done wrong, but other people may say revenge spells are morally wrong, because they believe that two wrongs do not make a right; and if they believe in karma, karma will bite that person back.
So that is just a post I thought would be rather interesting do to; while I had nothing to do. I hope this may have helped people with a few things.
Something else to keep in mind when writing a spell is the timing and correspondences associated with it. You may also want to cast your spell on a specific day or lunar cycle to help give it strength.
As for candles, candles do have their own correspondences and if you plan on using candles you might want to know what they are, unless you're using a white candle which is good for any spell. Using the wrong candle color might cause issues with spell casting. I've never done so, but if you use a pink candle (associated with love, friendship, etc) I would think that it wouldn't give you the end results you're looking for in a money spell which would call for, as previously stated, a green candle. The usage of candles is option though. They are more or less just a tool to help you focus on your intent, spell, etc. Still, it's always better to have the correct tool for the job (or in this case spell).