You don't actually need spells at all, you can create a magickal result with no words or items. Making spells yourself makes it a lot cheaper, especially if you don't inculde any items, but candles can be and often are, a powerful tool in all spells.
You can buy candles really cheaply and use them sparingly, only getting one large candle and then cleansing it between spells.
Alternatively an image of a candle could theoretically be used, especially if you are good with visualization.
I personally have used a candle app on a phone that can give the rather realistic version of a candle.
It all depends on why a spell needs a candle, if it is to represent the fire element then simply the colour red would do.
I am sorry I could not be of more assistance.