Okay so this is generally my opinion on this.A short post on the importance of some things.
You have decided you are going to use magic to solve the problem you have.You have looked through some spell books and varying other sites and keep hitting a bump in the road.Each spell requires items you don't have,can't get a hold of or can't use.To put the icing on top of the cake these spells must be done on a certain day,time,place and moon phase.Is all of that really important?
Almost everyone on this site will tell you it is definitely to omit somethings from a spell such as candles,oils,rose petals and such its not important you are.
Those items are there to aid you with your spell or to set the field.The items are used to enhance your spell by giving it some of its energy.So its not entirely important to have everything you can substitute or omit.
Substitute red ink pen for markers,paint,lipstick etc.Substitute ribbon for cord,thread,lacing or whatever you can think of.Substitute parchment paper with paper from your favorite book,colored paper matching your intention (colors affect your spell greatly so pay attention to what colors you are using)or fancy writing paper or any paper of good quality.
Is knowing your correspondences really important?
The days of the week,months of the year,planetary hours,moon phase and colors are all important things that should not be ignored as they can greatly affect the success of your spell especially if you are just starting off.
If a spell is needed to be done on a full moon just look for another spell that does not require this,as for the days of the week if a spell is to be said on a friday at a certain time of night and its monday don't fret just take note of what planet governed that hour on that day and wait for that planet's hour on monday and do your spell then.
The phases of the moon effects all spells.Each moon is used for specific range of spells pertaining to certain things just as the days of the week and months of the year.
The colors of cloth,pen ink,paper,candles,what you wear everyday and so on all affect you and your entire well being for that entire day.It also affects your spell work.Love spells use mainly red and money spells deal with the color green and so fort.You won't use green for a love spell as you would not use red for a money spell it won't work because you have used the wrong materials.
The question Is it really important boils down to two factors how important it is and whether you agree to use the method or not.