Essentials & Symbolism
Anything that is seen and done related to Ved or Vedic rituals has symbolic or spiritual meaning. Essentials are those which are must to perform specific rituals, some required items may not be available in some parts of the world, in such conditions optional items may be used.

 

There are many essential list of items that one needs to know, understand and own in order to regularly perform the Poojan and Vedic rituals. Following is an explanation of most of the items.
Shuddhi (Location, Body and Mind)
Cleansing of mind, body and location where you perform the rituals is must. 
Fasting
Refrain from Tamasik or rajasik food is must in order to focus and attain maximum benefits.
Celibacy (on the day of the Poojan OR during regular life)
Any materialistic or bodily pleasures can create hurdles for the Sadhna (penance), so staying away from such activites is must or highly preferred.
Prohibition of leather
Cow is considered as mother and holy in Vedic Sanatan Dharm, Panchgavya (5 things that can be received from cow) is part of any Yagna or routine rituals so leather is refrained.
Silence (away from any distraction)
Quietness within environment and also within is must to focus and get the best possible results 
Dhyaan (Focus)
Attentiveness at what you do during rituals and also while meditating is must
Fitness (Mental & Physical)
Willingness to perform or participate and physical ability to be involved for specific time period helps the purpose fulfilled.
Discipline
Rules and regulations must be maintained in order to complete the task smoothly.
Poojan Material
Each and all material that is part of the Vedic Poojan has specific purpose or reason to use and helps us attain the task completed properly.
Sequence
Each Specific Poojan or rituals has specific sequence which must be followed and can not be altered or changed until and unless there's compulsion based on situation or circumstances.
Disposal after completion
After the rituals are over, the flowers and leaves, grains, water and other material must be disposed appropriately so that it does not hurt the environment, nor it encroaches. 
Share & Care
Vedic Samskaar rituals are for optimum physical, mental, emotional and spiritual benefits and so it must be encouraged by supporting and sharing.
Donation
Donation towards the continuation of such activities should be done
Continuation
Just like we eat proper food, sleep enough, drink water on regular basis in order to keep us energetic and ongoing, we must have such religious rituals occurring on regular basis so our spiritual uplifting happens.