Any type of magick doesn't really need to be " costly ". Spells do not need to be big chants, neither do they need to have a long list of ingredients. As for the " easy " part, none is. Because you need to know the basics of magick itself and then decide on which branch you would like to go for, be it knot magick, candle magick, etc.
A lot of people also defend that you making your own spells will make the more effective as you are pouring your energy in to them. So in this case, you can always create a spell that isn't too costly, yet effective ( as long as it is realistic of course ).